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 crafted request uri-path can cause modproxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.

A flaw was found in the logback package. When using a specially-crafted configuration, this issue could allow a remote authenticated attacker to execute arbitrary code loaded from LDAP servers.

A vulnerability has been identified in SINEC NMS (All versions < V2.0 SP1). The affected application incorrectly neutralizes special elements when creating a report which could lead to command injection.

A vulnerability has been identified in SINEC NMS (All versions < V2.0 SP1). The affected application allows users to upload arbitrary files via TFTP. This could allow an attacker to upload malicious firmware images or other files, that could potentially lead to remote code execution.

A vulnerability has been identified in SINEC NMS (All versions < V2.0 SP1). The affected application is vulnerable to SQL injection. This could allow an unauthenticated remote attacker to execute arbitrary SQL queries on the server database.

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signaturealgorithms extension (where it was present in the initial ClientHello), but includes a signaturealgorithmscert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j).

An out-of-bounds write in function apescapequotes of httpd allows an unauthenticated remote attacker to crash the server or potentially execute code on the system with the privileges of the httpd user, by providing malicious input to the function.

A vulnerability has been identified in Security Configuration Tool (SCT) (All versions), SIMATIC Automation Tool (All versions < V5.0 SP2), SIMATIC BATCH V9.1 (All versions < V9.1 SP2 Upd5), SIMATIC NET PC Software V16 (All versions < V16 Update 8), SIMATIC NET PC Software V17 (All versions), SIMATIC NET PC Software V18 (All versions < V18 SP1), SIMATIC NET PC Software V19 (All versions < V19 Update 2), SIMATIC PCS 7 V9.1 (All versions < V9.1 SP2 UC05), SIMATIC PDM V9.2 (All versions < V9.2 SP2 Upd3), SIMATIC Route Control V9.1 (All versions < V9.1 SP2 Upd3), SIMATIC S7-PCT (All versions < V3.5 SP3 Update 6), SIMATIC STEP 7 V5 (All versions < V5.7 SP3), SIMATIC WinCC OA V3.17 (All versions), SIMATIC WinCC OA V3.18 (All versions < V3.18 P025), SIMATIC WinCC OA V3.19 (All versions < V3.19 P010), SIMATIC WinCC Runtime Advanced (All versions < V17 Update 8), SIMATIC WinCC Runtime Professional V16 (All versions < V16 Update 6), SIMATIC WinCC Runtime Professional V17 (All versions < V17 Update 8), SIMATIC WinCC Runtime Professional V18 (All versions < V18 Update 4), SIMATIC WinCC Runtime Professional V19 (All versions < V19 Update 2), SIMATIC WinCC V7.4 (All versions), SIMATIC WinCC V7.5 (All versions < V7.5 SP2 Update 17), SIMATIC WinCC V8.0 (All versions < V8.0 Update 5), SINAMICS Startdrive (All versions < V19 SP1), SINEC NMS (All versions < V3.0), SINUMERIK ONE virtual (All versions < V6.23), SINUMERIK PLC Programming Tool (All versions < V3.3.12), TIA Portal Cloud Connector (All versions < V2.0), Totally Integrated Automation Portal (TIA Portal) V15.1 (All versions), Totally Integrated Automation Portal (TIA Portal) V16 (All versions), Totally Integrated Automation Portal (TIA Portal) V17 (All versions < V17 Update 8), Totally Integrated Automation Portal (TIA Portal) V18 (All versions < V18 Update 4), Totally Integrated Automation Portal (TIA Portal) V19 (All versions < V19 Update 2), SINEC NMS (All versions < V3.0 SP1). The affected applications contain an out of bounds read vulnerability. This could allow an attacker to cause a Blue Screen of Death (BSOD) crash of the underlying Windows kernel.

A NULL pointer dereference in httpd allows an unauthenticated remote attacker to crash httpd by providing malformed HTTP requests. The highest threat from this vulnerability is to system availability.

This vulnerability allows remote attackers to escalate privileges on affected installations of Siemens SINEC NMS. Authentication is required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.8. The following CVEs are assigned: CVE-2026-25654.

This vulnerability allows remote attackers to escalate privileges on affected installations of Siemens SINEC NMS. Authentication is required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.8. The following CVEs are assigned: CVE-2026-25654.

This vulnerability allows remote attackers to bypass authentication on affected installations of Siemens SINEC NMS. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.3. The following CVEs are assigned: CVE-2026-24032.

This vulnerability allows remote attackers to bypass authentication on affected installations of Siemens SINEC NMS. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.3. The following CVEs are assigned: CVE-2026-24032.

A vulnerability has been identified in SINEC NMS (All versions < V4.0 SP3). Affected products do not properly validate user authorization when processing password reset requests. This could allow an authenticated remote attacker to bypass authorization checks, leading to the ability to reset the password of any arbitrary user account.

A vulnerability has been identified in SINEC NMS (All versions < V2.0 SP2). Affected devices allow authenticated users to export monitoring data. The corresponding API endpoint is susceptible to path traversal and could allow an authenticated attacker to download files from the file system. Under certain circumstances the downloaded files are deleted from the file system.

A vulnerability has been identified in SINEC NMS (All versions < V4.0 SP3), User Management Component (UMC) (All versions < V2.15.2.1). The affected application permits improper modification of a configuration file by a low-privileged user. This could allow an attacker to load malicious DLLs, potentially leading to arbitrary code execution with SYSTEM privileges.(ZDI-CAN-28108)

This vulnerability allows local attackers to escalate privileges on affected installations of Siemens SINEC NMS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.8. The following CVEs are assigned: CVE-2026-25656.

This vulnerability allows local attackers to escalate privileges on affected installations of Siemens SINEC NMS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.8. The following CVEs are assigned: CVE-2026-25656.

This vulnerability allows local attackers to escalate privileges on affected installations of Siemens SINEC NMS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.8. The following CVEs are assigned: CVE-2026-25655.

This vulnerability allows local attackers to escalate privileges on affected installations of Siemens SINEC NMS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.8. The following CVEs are assigned: CVE-2026-25655.

A vulnerability has been identified in SINEC NMS (All versions < V4.0 SP2). The affected application permits improper modification of a configuration file by a low-privileged user. This could allow an attacker to load malicious DLLs, potentially leading to arbitrary code execution with administrative privilege.(ZDI-CAN-28107)

A vulnerability has been identified in Opcenter Execution Foundation (All versions < V2501.0001), Opcenter Intelligence (All versions < V2501.0001), Opcenter Quality (All versions < V2512), Opcenter RDnL (All versions < V2410), SIMATIC PCS neo V4.0 (All versions), SIMATIC PCS neo V4.1 (All versions < V4.1 Update 3), SIMATIC PCS neo V5.0 (All versions < V5.0 Update 1), SINEC NMS (All versions if operated in conjunction with UMC < V2.15), Totally Integrated Automation Portal (TIA Portal) V16 (All versions), Totally Integrated Automation Portal (TIA Portal) V17 (All versions), Totally Integrated Automation Portal (TIA Portal) V18 (All versions), Totally Integrated Automation Portal (TIA Portal) V19 (All versions). Affected products contain a heap-based buffer overflow vulnerability in the integrated UMC component. This could allow an unauthenticated remote attacker to execute arbitrary code.

A vulnerability has been identified in SINEC NMS (All versions < V1.0.3), SINEMA Server V14 (All versions). A privileged authenticated attacker could execute arbitrary commands in the local database by sending specially crafted requests to the webserver of the affected application.

A vulnerability has been identified in SINEC NMS (All versions >= V1.0.3 < V2.0), SINEC NMS (All versions < V1.0.3), SINEMA Server V14 (All versions). The affected system allows to upload JSON objects that are deserialized to Java objects. Due to insecure deserialization of user-supplied content by the affected software, a privileged attacker could exploit this vulnerability by sending a maliciously crafted serialized Java object. This could allow the attacker to execute arbitrary code on the device with root privileges.

A vulnerability has been identified in SINEC NMS (All versions >= V1.0.3 < V2.0), SINEC NMS (All versions < V1.0.3), SINEMA Server V14 (All versions). The affected software do not properly check privileges between users during the same web browser session, creating an unintended sphere of control. This could allow an authenticated low privileged user to achieve privilege escalation.

A vulnerability has been identified in SINEC NMS (All versions < V1.0 SP2). The affected application incorrectly neutralizes special elements when creating batch operations which could lead to command injection. An authenticated remote attacker with administrative privileges could exploit this vulnerability to execute arbitrary code on the system with system privileges.