Summary

Terrapin is a prefix truncation attack targeting the SSH protocol. More precisely, Terrapin breaks the integrity of SSH's secure channel. By carefully adjusting the sequence numbers during the handshake, an attacker can remove an arbitrary amount of messages sent by the client or server at the beginning of the secure channel without the client or server noticing it.

Mitigations

To mitigate this protocol vulnerability, OpenSSH suggested a so-called "strict kex" which alters the SSH handshake to ensure a Man-in-the-Middle attacker cannot introduce unauthenticated messages as well as convey sequence number manipulation across handshakes.

Warning: To take effect, both the client and server must support this countermeasure.

As a stop-gap measure, peers may also (temporarily) disable the affected algorithms and use unaffected alternatives like AES-GCM instead until patches are available.

Details

The SSH specifications of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com MACs) are vulnerable against an arbitrary prefix truncation attack (a.k.a. Terrapin attack). This allows for an extension negotiation downgrade by stripping the SSHMSGEXTINFO sent after the first message after SSHMSGNEWKEYS, downgrading security, and disabling attack countermeasures in some versions of OpenSSH. When targeting Encrypt-then-MAC, this attack requires the use of a CBC cipher to be practically exploitable due to the internal workings of the cipher mode. Additionally, this novel attack technique can be used to exploit previously unexploitable implementation flaws in a Man-in-the-Middle scenario.

The attack works by an attacker injecting an arbitrary number of SSHMSGIGNORE messages during the initial key exchange and consequently removing the same number of messages just after the initial key exchange has concluded. This is possible due to missing authentication of the excess SSHMSGIGNORE messages and the fact that the implicit sequence numbers used within the SSH protocol are only checked after the initial key exchange.

In the case of ChaCha20-Poly1305, the attack is guaranteed to work on every connection as this cipher does not maintain an internal state other than the message's sequence number. In the case of Encrypt-Then-MAC, practical exploitation requires the use of a CBC cipher; while theoretical integrity is broken for all ciphers when using this mode, message processing will fail at the application layer for CTR and stream ciphers.

For more details see https://terrapin-attack.com.

Impact

This attack targets the specification of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com), which are widely adopted by well-known SSH implementations and can be considered de-facto standard. These algorithms can be practically exploited; however, in the case of Encrypt-Then-MAC, we additionally require the use of a CBC cipher. As a consequence, this attack works against all well-behaving SSH implementations supporting either of those algorithms and can be used to downgrade (but not fully strip) connection security in case SSH extension negotiation (RFC8308) is supported. The attack may also enable attackers to exploit certain implementation flaws in a man-in-the-middle (MitM) scenario.

A privilege escalation vulnerability in Palo Alto Networks PAN-OS software allows a PAN-OS administrator with access to the management web interface to perform actions on the firewall with root privileges.

Cloud NGFW and Prisma Access are not impacted by this vulnerability.

An authentication bypass in Palo Alto Networks PAN-OS software enables an unauthenticated attacker with network access to the management web interface to gain PAN-OS administrator privileges to perform administrative actions, tamper with the configuration, or exploit other authenticated privilege escalation vulnerabilities like CVE-2024-9474 https://security.paloaltonetworks.com/CVE-2024-9474 .

The risk of this issue is greatly reduced if you secure access to the management web interface by restricting access to only trusted internal IP addresses according to our recommended  best practice deployment guidelines https://live.paloaltonetworks.com/t5/community-blogs/tips-amp-tricks-how-to-secure-the-management-access-of-your-palo/ba-p/464431 .

This issue is applicable only to PAN-OS 10.2, PAN-OS 11.0, PAN-OS 11.1, and PAN-OS 11.2 software.

Cloud NGFW and Prisma Access are not impacted by this vulnerability.

An authenticated file read vulnerability in the management web interface of the Palo Alto Networks PAN-OS software enables an authenticated attacker with network access to the management web interface to read files on the PAN-OS filesystem that are readable by the “nobody” user.

The attacker must have network access to the management web interface to exploit this issue. You can greatly reduce the risk of this issue by restricting access to the management web interface to only trusted internal IP addresses according to our recommended critical deployment guidelines (https://live.paloaltonetworks.com/t5/community-blogs/tips-amp-tricks-how-to-secure-the-management-access-of-your-palo/ba-p/464431).

This issue does not affect Cloud NGFW or Prisma Access software.

An improper input validation vulnerability in Palo Alto Networks PAN-OS software enables an attacker with the ability to tamper with the physical file system to elevate privileges.

A command injection as a result of arbitrary file creation vulnerability in the GlobalProtect feature of Palo Alto Networks PAN-OS software for specific PAN-OS versions and distinct feature configurations may enable an unauthenticated attacker to execute arbitrary code with root privileges on the firewall.

Cloud NGFW, Panorama appliances, and Prisma Access are not impacted by this vulnerability.

A vulnerability exists in Palo Alto Networks PAN-OS software that enables an authenticated administrator with the privilege to commit a specifically created configuration to read local files and resources from the system.

A fundamental design flaw within the RADIUS protocol has been proven to be exploitable, compromising the integrity in the RADIUS Access-Request process. The attack allows a malicious user to modify packets in a way that would be indistinguishable to a RADIUS client or server. To be successful, the attacker must have the ability to inject themselves between the client and server.

A packet processing mechanism in Palo Alto Networks PAN-OS software enables a remote attacker to reboot hardware-based firewalls. Repeated attacks eventually cause the firewall to enter maintenance mode, which requires manual intervention to bring the firewall back online.

This affects the following hardware firewall models: - PA-5400 Series firewalls - PA-7000 Series firewalls

An improper authorization vulnerability in Palo Alto Networks Panorama software enables an authenticated read-only administrator to upload files using the web interface and completely fill one of the disk partitions with those uploaded files, which prevents the ability to log into the web interface or to download PAN-OS, WildFire, and content images.

This issue affects only the web interface of the management plane; the dataplane is unaffected.

A memory leak exists in Palo Alto Networks PAN-OS software that enables an attacker to send a burst of crafted packets through the firewall that eventually prevents the firewall from processing traffic. This issue applies only to PA-5400 Series devices that are running PAN-OS software with the SSL Forward Proxy feature enabled.

An incorrect string comparison vulnerability in Palo Alto Networks PAN-OS software prevents Predefined Decryption Exclusions from functioning as intended. This can cause traffic destined for domains that are not specified in Predefined Decryption Exclusions to be unintentionally excluded from decryption.

A command injection vulnerability in Palo Alto Networks PAN-OS® enables an authenticated administrative user to perform actions as the root user.

The attacker must have network access to the management web interface and successfully authenticate to exploit this issue.

Cloud NGFW and Prisma Access are not impacted by this vulnerability.

A credential disclosure vulnerability in Palo Alto Networks PAN-OS software enables an authenticated read-only administrator to obtain the plaintext credentials of stored external system integrations such as LDAP, SCP, RADIUS, TACACS+, and SNMP from the web interface.

A weak (low bit strength) device certificate in Palo Alto Networks Panorama software enables an attacker to perform a meddler-in-the-middle (MitM) attack to capture encrypted traffic between the Panorama management server and the firewalls it manages. With sufficient computing resources, the attacker could break encrypted communication and expose sensitive information that is shared between the management server and the firewalls.

A cross-site scripting (XSS) vulnerability in Palo Alto Networks PAN-OS software enables an authenticated read-write Panorama administrator to push a specially crafted configuration to a PAN-OS node. This enables impersonation of a legitimate PAN-OS administrator who can perform restricted actions on the PAN-OS node after the execution of JavaScript in the legitimate PAN-OS administrator's browser.

An information exposure vulnerability in Palo Alto Networks PAN-OS software enables a local system administrator to unintentionally disclose secrets, passwords, and tokens of external systems. A read-only administrator who has access to the config log, can read secrets, passwords, and tokens to external systems.

Web sessions in the management interface in Palo Alto Networks PAN-OS software do not expire in certain situations, making it susceptible to unauthorized access.

A file disclosure vulnerability in Palo Alto Networks PAN-OS software enables an authenticated read-write administrator with access to the web interface to export local files from the firewall through a race condition.

A vulnerability in the GlobalProtect Gateway in Palo Alto Networks PAN-OS software enables an authenticated attacker to impersonate another user and send network packets to internal assets. However, this vulnerability does not allow the attacker to receive response packets from those internal assets.

A blind XML External Entities (XXE) injection vulnerability in the Palo Alto Networks PAN-OS software enables an authenticated attacker to exfiltrate arbitrary files from firewalls to an attacker controlled server. This attack requires network access to the firewall management interface.

A command injection vulnerability in Palo Alto Networks PAN-OS software enables an authenticated administrator to bypass system restrictions in the management plane and delete files on the firewall.

A null pointer dereference vulnerability in Palo Alto Networks PAN-OS software enables an unauthenticated attacker to stop a core system service on the firewall by sending a crafted packet through the data plane that causes a denial of service (DoS) condition. Repeated attempts to trigger this condition result in the firewall entering maintenance mode.

A null pointer dereference vulnerability in the GlobalProtect gateway in Palo Alto Networks PAN-OS software enables an unauthenticated attacker to stop the GlobalProtect service on the firewall by sending a specially crafted packet that causes a denial of service (DoS) condition. Repeated attempts to trigger this condition result in the firewall entering maintenance mode.

A vulnerability in how Palo Alto Networks PAN-OS software processes data received from Cloud Identity Engine (CIE) agents enables modification of User-ID groups. This impacts user access to network resources where users may be inappropriately denied or allowed access to resources based on your existing Security Policy rules.

An improper verification vulnerability in the GlobalProtect gateway feature of Palo Alto Networks PAN-OS software enables a malicious user with stolen credentials to establish a VPN connection from an unauthorized IP address.

An improper privilege management vulnerability in Palo Alto Networks PAN-OS software enables an authenticated read-only administrator to revoke active XML API keys from the firewall and disrupt XML API usage.

A privilege escalation (PE) vulnerability in the XML API of Palo Alto Networks PAN-OS software enables an authenticated PAN-OS administrator with restricted privileges to use a compromised XML API key to perform actions as a higher privileged PAN-OS administrator beyond what the XML API permits.

An information exposure vulnerability exists in Palo Alto Networks PAN-OS software that enables a GlobalProtect end user to learn both the configured GlobalProtect uninstall password and the configured disable or disconnect passcode. After the password or passcode is known, end users can uninstall, disable, or disconnect GlobalProtect even if the GlobalProtect app configuration would not normally permit them to do so.

A DOM-Based cross-site scripting (XSS) vulnerability in Palo Alto Networks PAN-OS software enables a remote attacker to execute a JavaScript payload in the context of an administrator’s browser when they view a specifically crafted link to the PAN-OS web interface.