HTTP/2 Rapid reset attack The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RSTSTREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RSTSTREAM frame, before any other data from that TCP connection is processed.

Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RSTSTREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.

The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.

The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.

In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RSTSTREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.

Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the swift-nio-http2 repo advisory and their original conent follows.

swift-nio-http2 specific advisory swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new Channels to serve the traffic. This can easily overwhelm an EventLoop and prevent it from making forward progress.

swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.

A Denial of Service vulnerability in the remote login functionality for Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. The attacker could use either a Telnet or an SSH client for the remote login attempt. Affected Products: This vulnerability affects Cisco Nexus 9000 Series Switches that are running Cisco NX-OS Software and are configured to allow remote Telnet connections to the device. More Information: CSCuy25824. Known Affected Releases: 7.0(3)I3(1) 8.3(0)CV(0.342) 8.3(0)CV(0.345). Known Fixed Releases: 8.3(0)CV(0.362) 8.0(1) 7.0(3)IED5(0.19) 7.0(3)IED5(0) 7.0(3)I4(1) 7.0(3)I4(0.8) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1) 7.0(3)F1(0.230).

A Denial of Service vulnerability in the Telnet remote login functionality of Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a Telnet process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. Affected Products: This vulnerability affects Cisco Nexus 9000 Series Switches that are running Cisco NX-OS Software and are configured to allow remote Telnet connections to the device. More Information: CSCux46778. Known Affected Releases: 7.0(3)I3(0.170). Known Fixed Releases: 7.0(3)I3(1) 7.0(3)I3(0.257) 7.0(3)I3(0.255) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1).

IP-in-IP protocol specifies IP Encapsulation within IP standard (RFC 2003, STD 1) that decapsulate and route IP-in-IP traffic is vulnerable to spoofing, access-control bypass and other unexpected behavior due to the lack of validation to verify network packets before decapsulation and routing.

A vulnerability in the Link Layer Discovery Protocol (LLDP) feature of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of specific fields in an LLDP frame. An attacker could exploit this vulnerability by sending a crafted LLDP packet to an interface of an affected device and having an authenticated user retrieve LLDP statistics from the affected device through CLI show commands or Simple Network Management Protocol (SNMP) requests. A successful exploit could allow the attacker to cause the LLDP service to crash and stop running on the affected device. In certain situations, the LLDP crash may result in a reload of the affected device. Note: LLDP is a Layer 2 link protocol. To exploit this vulnerability, an attacker would need to be directly connected to an interface of an affected device, either physically or logically (for example, through a Layer 2 Tunnel configured to transport the LLDP protocol).

A vulnerability in the access control list (ACL) programming for port channel subinterfaces of Cisco Nexus 3000 and 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to send traffic that should be blocked through an affected device. This vulnerability is due to incorrect hardware programming that occurs when configuration changes are made to port channel member ports. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to access network resources that should be protected by an ACL that was applied on port channel subinterfaces.

A vulnerability in the implementation of a specific CLI command and the associated Simple Network Management Protocol (SNMP) MIB for Cisco NX-OS (in standalone NX-OS mode) on Cisco Nexus 3000 and 9000 Series Switches could allow an authenticated, remote attacker to exhaust system memory on an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to the incorrect implementation of the CLI command, resulting in a failure to free all allocated memory upon completion. An attacker could exploit this vulnerability by authenticating to the affected device and repeatedly issuing a specific CLI command or sending a specific SNMP poll request for a specific Object Identifier (OID). A successful exploit could allow the attacker to cause the IP routing process to restart or to cause a device reset, resulting in a DoS condition. Cisco Bug IDs: CSCvf23136.

A vulnerability in the management interface of Cisco Application Policy Infrastructure Controller (APIC) software could allow an unauthenticated, adjacent attacker to gain unauthorized access on an affected device. The vulnerability is due to a lack of proper access control mechanisms for IPv6 link-local connectivity imposed on the management interface of an affected device. An attacker on the same physical network could exploit this vulnerability by attempting to connect to the IPv6 link-local address on the affected device. A successful exploit could allow the attacker to bypass default access control restrictions on an affected device. Cisco Application Policy Infrastructure Controller (APIC) devices running versions prior to 4.2(0.21c) are affected.

A vulnerability in Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an authenticated, remote attacker to access sensitive information. The vulnerability occurs because the affected software does not properly validate user-supplied input. An attacker could exploit this vulnerability by issuing certain commands with filtered query results on the device. This action may cause returned messages to display confidential system information. A successful exploit could allow the attacker to read sensitive information on the device.

A vulnerability in the Trusted Platform Module (TPM) functionality of software for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, local attacker with physical access to view sensitive information on an affected device. The vulnerability is due to a lack of proper data-protection mechanisms for disk encryption keys that are used within the partitions on an affected device hard drive. An attacker could exploit this vulnerability by obtaining physical access to the affected device to view certain cleartext keys. A successful exploit could allow the attacker to execute a custom boot process or conduct further attacks on an affected device.

A vulnerability in the SSH CLI key management functionality of Cisco NX-OS Software could allow an authenticated, local attacker to expose a user's private SSH key to all authenticated users on the targeted device. The attacker must authenticate with valid administrator device credentials. The vulnerability is due to incomplete error handling if a specific error type occurs during the SSH key export. An attacker could exploit this vulnerability by authenticating to the device and entering a crafted command at the CLI. A successful exploit could allow the attacker to expose a user's private SSH key. In addition, a similar type of error in the SSH key import could cause the passphrase-protected private SSH key to be imported unintentionally.

A vulnerability in the Bash shell implementation for Cisco NX-OS Software could allow an authenticated, local attacker to bypass the limited command set of the restricted Guest Shell and execute commands at the privilege level of a network-admin user outside of the Guest Shell. The attacker must authenticate with valid administrator device credentials. The vulnerability is due to the incorrect implementation of a CLI command that allows a Bash command to be incorrectly invoked on the Guest Shell CLI. An attacker could exploit this vulnerability by authenticating to the device and entering a crafted command at the Guest Shell prompt. A successful exploit could allow the attacker to issue commands that should be restricted by a Guest Shell account.

A vulnerability in the CLI of Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands with elevated privileges on the underlying operating system of an affected device. The vulnerability is due to insufficient validation of arguments passed to certain CLI commands. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with elevated privileges. An attacker would need valid user credentials to exploit this vulnerability.

A vulnerability in the CLI of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands on the underlying operating system of an affected device with elevated privileges. The vulnerability is due to insufficient validation of arguments passed to certain CLI commands. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with elevated privileges. An attacker would need valid device credentials to exploit this vulnerability.

A vulnerability in the CLI of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker with administrator credentials to execute arbitrary commands on the underlying operating system of an affected device with elevated privileges. The vulnerability is due to insufficient validation of arguments passed to certain CLI commands. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with elevated privileges. An attacker would need valid administrator credentials to exploit this vulnerability. NX-OS versions prior to 8.3(1) are affected. NX-OS versions prior to 8.3(1) are affected.

A vulnerability within the Endpoint Learning feature of Cisco Nexus 9000 Series Switches running in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an endpoint device in certain circumstances. The vulnerability is due to improper endpoint learning when packets are received on a specific port from outside the ACI fabric and destined to an endpoint located on a border leaf when Disable Remote Endpoint Learning has been enabled. This can result in a Remote (XR) entry being created for the impacted endpoint that will become stale if the endpoint migrates to a different port or leaf switch. This results in traffic not reaching the impacted endpoint until the Remote entry can be relearned by another mechanism.

A vulnerability in the implementation of a CLI diagnostic command in Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to view sensitive system files that should be restricted. The attacker could use this information to conduct additional reconnaissance attacks. The vulnerability is due to incomplete role-based access control (RBAC) verification. An attacker could exploit this vulnerability by authenticating to the device and issuing a specific CLI diagnostic command with crafted user-input parameters. An exploit could allow the attacker to perform an arbitrary read of a file on the device, and the file may contain sensitive information. The attacker needs valid device credentials to exploit this vulnerability.

A vulnerability in the filesystem management for the Cisco Nexus 9000 Series Application Centric Infrastructure (ACI) Mode Switch Software could allow an authenticated, local attacker with administrator rights to gain elevated privileges as the root user on an affected device. The vulnerability is due to overly permissive file permissions of specific system files. An attacker could exploit this vulnerability by authenticating to an affected device, creating a crafted command string, and writing this crafted string to a specific file location. A successful exploit could allow the attacker to execute arbitrary operating system commands as root on an affected device. The attacker would need to have valid administrator credentials for the device.

A vulnerability in the background operations functionality of Cisco Nexus 9000 Series Application Centric Infrastructure (ACI) Mode Switch Software could allow an authenticated, local attacker to gain elevated privileges as root on an affected device. The vulnerability is due to insufficient validation of user-supplied files on an affected device. An attacker could exploit this vulnerability by logging in to the CLI of the affected device and creating a crafted file in a specific directory on the filesystem. A successful exploit could allow the attacker to execute arbitrary operating system commands as root on an affected device.

A vulnerability in the Transport Layer Security (TLS) certificate validation functionality of Cisco Nexus 9000 Series Application Centric Infrastructure (ACI) Mode Switch Software could allow an unauthenticated, remote attacker to perform insecure TLS client authentication on an affected device. The vulnerability is due to insufficient TLS client certificate validations for certificates sent between the various components of an ACI fabric. An attacker who has possession of a certificate that is trusted by the Cisco Manufacturing CA and the corresponding private key could exploit this vulnerability by presenting a valid certificate while attempting to connect to the targeted device. An exploit could allow the attacker to gain full control of all other components within the ACI fabric of an affected device.

A vulnerability in the implementation of a specific CLI command for Cisco NX-OS Software could allow an authenticated, local attacker with administrator credentials to cause a buffer overflow condition or perform command injection. This could allow the attacker to execute arbitrary commands with elevated privileges on the underlying operating system of an affected device. The vulnerability is due to insufficient validation of arguments passed to a certain CLI command. An attacker could exploit this vulnerability by including malicious input as the argument of the affected CLI command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with root privileges. An attacker would need valid administrator credentials to exploit these vulnerabilities. NX-OS versions prior to 8.3(1) are affected.

A vulnerability in the CLI of Cisco NX-OS Software could allow an authenticated, local attacker with administrator credentials to execute arbitrary commands on the underlying Linux operating system of an attached line card with the privilege level of root. The vulnerability is due to insufficient validation of arguments passed to a specific CLI command on the affected device. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux operating system of an attached line card with elevated privileges. An attacker would need valid administrator credentials to exploit this vulnerability.

A vulnerability in the CLI of Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands on the underlying Linux operating system with the privilege level of root. The vulnerability is due to insufficient validation of arguments passed to a specific CLI command on the affected device. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux operating system with elevated privileges. An attacker would need valid administrator credentials to exploit this vulnerability.

A vulnerability in the CLI of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands on the underlying operating system of an affected device. This vulnerability is due to insufficient validation of arguments passed to certain CLI commands. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with elevated privileges. An attacker would need administrator credentials to exploit this vulnerability.

A vulnerability in the CLI of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands on the underlying operating system of an affected device. This vulnerability is due to insufficient validation of arguments passed to certain CLI commands. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with elevated privileges. An attacker would need administrator credentials to exploit this vulnerability.

A vulnerability in the implementation of a specific CLI command for Cisco NX-OS Software could allow an authenticated, local attacker with administrator credentials to cause a buffer overflow condition or perform command injection. This could allow the attacker to execute arbitrary commands with elevated privileges on the underlying operating system of an affected device. The vulnerability is due to insufficient validation of arguments passed to a certain CLI command. An attacker could exploit this vulnerability by including malicious input as the argument of the affected CLI command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with root privileges. An attacker would need valid administrator credentials to exploit these vulnerabilities.

A vulnerability in the Link Layer Discovery Protocol (LLDP) subsystem of Cisco Nexus 9000 Series Application Centric Infrastructure (ACI) Mode Switch Software could allow an adjacent, unauthenticated attacker to cause a denial of service (DoS) condition or execute arbitrary code with root privileges. The vulnerability is due to improper input validation of certain type, length, value (TLV) fields of the LLDP frame header. An attacker could exploit this vulnerability by sending a crafted LLDP packet to the targeted device. A successful exploit may lead to a buffer overflow condition that could either cause a DoS condition or allow the attacker to execute arbitrary code with root privileges. Note: This vulnerability cannot be exploited by transit traffic through the device; the crafted packet must be targeted to a directly connected interface. This vulnerability affects Cisco Nexus 9000 Series Fabric Switches in ACI mode if they are running a Cisco Nexus 9000 Series ACI Mode Switch Software release prior to 13.2(7f) or any 14.x release.

A vulnerability in Cisco NX-OS Software and Cisco IOS XE Software could allow an authenticated, local attacker with valid administrator or privilege level 15 credentials to load a virtual service image and bypass signature verification on an affected device. The vulnerability is due to improper signature verification during the installation of an Open Virtual Appliance (OVA) image. An authenticated, local attacker could exploit this vulnerability and load a malicious, unsigned OVA image on an affected device. A successful exploit could allow an attacker to perform code execution on a crafted software OVA image.

A vulnerability in a CLI command related to the virtualization manager (VMAN) in Cisco NX-OS Software could allow an authenticated, local attacker to execute arbitrary commands on the underlying Linux operating system with root privileges. The vulnerability is due to insufficient validation of arguments passed to a specific VMAN CLI command on an affected device. An attacker could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux operating system with root privileges, which may lead to complete system compromise. An attacker would need valid administrator credentials to exploit this vulnerability.

A vulnerability in the Network Time Protocol (NTP) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to excessive use of system resources when the affected device is logging a drop action for received MODEPRIVATE (Mode 7) NTP packets. An attacker could exploit this vulnerability by flooding the device with a steady stream of Mode 7 NTP packets. A successful exploit could allow the attacker to cause high CPU and memory usage on the affected device, which could cause internal system processes to restart or cause the affected device to unexpectedly reload. Note: The NTP feature is enabled by default.