A security regression (CVE-2006-5051) was discovered in OpenSSH's server (sshd). There is a race condition which can lead sshd to handle some signals in an unsafe manner. An unauthenticated, remote attacker may be able to trigger it by failing to authenticate within a set time period.

A authentication bypass using an alternate path or channel vulnerability in Fortinet FortiManager 7.6.1, FortiManager 7.4.3 through 7.4.5, FortiManager 7.2.5 through 7.2.9, FortiManager Cloud 7.6.1, FortiManager Cloud 7.4.3 through 7.4.5, FortiManager Cloud 7.2.5 through 7.2.9 may allow attacker to improper access control via <insert attack vector here>

An improper neutralization of special elements used in an SQL command ('SQL injection') [CWE-89] in FortiAnalyzer, FortiAnalyzer Cloud, FortiManager and FortiManager Cloud may allow an authenticated privileged attacker to execute unauthorized code or commands via crafted requests.

A client-side enforcement of server-side security [CWE-602] vulnerability in FortiManager and FortiAnalyzer may allow a remote attacker with low privileges to access a privileged web console via client side code execution.

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 improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiManager 7.6.0 through 7.6.1, FortiManager 7.4.1 through 7.4.3, FortiManager Cloud 7.4.1 through 7.4.3, FortiOS 7.6.0, FortiOS 7.4.0 through 7.4.4, FortiOS 7.2.0 through 7.2.9, FortiOS 7.0.0 through 7.0.15, FortiOS 6.4.0 through 6.4.15, FortiProxy 7.4.0 through 7.4.5, FortiProxy 7.2.0 through 7.2.11, FortiProxy 7.0.0 through 7.0.18, FortiProxy 2.0 all versions, FortiProxy 1.2 all versions, FortiProxy 1.1 all versions, FortiProxy 1.0 all versions may allow a remote authenticated attacker with access to the security fabric interface and port to write arbitrary files or a remote unauthenticated attacker to delete an arbitrary folder

A incorrect privilege assignment vulnerability in Fortinet FortiAnalyzer 7.4.0 through 7.4.3, FortiAnalyzer 7.2.0 through 7.2.5, FortiAnalyzer 7.0 all versions, FortiAnalyzer 6.4 all versions, FortiAnalyzer Cloud 7.4.1 through 7.4.2, FortiAnalyzer Cloud 7.2.1 through 7.2.6, FortiAnalyzer Cloud 7.0 all versions, FortiAnalyzer Cloud 6.4 all versions, FortiManager 7.4.0 through 7.4.3, FortiManager 7.2.0 through 7.2.5, FortiManager 7.0 all versions, FortiManager 6.4 all versions allows attacker to escalate privilege via specific shell commands

A improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiRecorder 7.2.0 through 7.2.1, FortiRecorder 7.0.0 through 7.0.4, FortiVoice 7.0.0 through 7.0.4, FortiVoice 6.4.0 through 6.4.9, FortiVoice 6.0 all versions, FortiWeb 7.6.0, FortiWeb 7.4.0 through 7.4.4, FortiWeb 7.2 all versions, FortiWeb 7.0 all versions, FortiWeb 6.4 all versions allows attacker to escalate privilege via specially crafted packets.

A stack-based buffer overflow vulnerability in Fortinet FortiAnalyzer 7.4.0 through 7.4.3, FortiAnalyzer 7.2.0 through 7.2.5, FortiAnalyzer 7.0.0 through 7.0.12, FortiAnalyzer 6.4.0 through 6.4.14, FortiAnalyzer Cloud 7.4.1 through 7.4.3, FortiAnalyzer Cloud 7.2.1 through 7.2.5, FortiAnalyzer Cloud 7.0.1 through 7.0.11, FortiAnalyzer Cloud 6.4 all versions, FortiManager 7.4.0 through 7.4.3, FortiManager 7.2.0 through 7.2.5, FortiManager 7.0.0 through 7.0.12, FortiManager 6.4.0 through 6.4.14, FortiManager Cloud 7.4.1 through 7.4.3, FortiManager Cloud 7.2.1 through 7.2.5, FortiManager Cloud 7.0.1 through 7.0.11, FortiManager Cloud 6.4 all versions allows attacker to execute unauthorized code or commands via specially crafted packets.

A improper privilege management vulnerability in Fortinet FortiManager Cloud 7.4.1 through 7.4.3, FortiManager Cloud 7.2.1 through 7.2.5, FortiManager Cloud 7.0 all versions, FortiManager 7.4.0 through 7.4.3, FortiManager 7.2.0 through 7.2.5, FortiManager 7.0 all versions, FortiManager 6.4 all versions allows attacker to escalation of privilege via specific shell commands

A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack.

An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] in FortiOS, FortiManager, FortiAnalyzer, FortiProxy, FortiSwitchManager, FortiWeb may allow an attacker with a FortiCloud account and a registered device to log into other devices registered to other accounts, if FortiCloud SSO authentication is enabled on those devices.Please note that the FortiCloud SSO login feature is not enabled in default factory settings. However, when an administrator registers the device to FortiCare from the device's GUI, unless the administrator disables the toggle switch "Allow administrative login using FortiCloud SSO" in the registration page, FortiCloud SSO login is enabled upon registration. This vulnerability was found being exploited in the wild by two malicious FortiCloud accounts, which were locked out on 2026-01-22. In order to protect its customers from further exploit, Fortinet disabled FortiCloud SSO on FortiCloud side on 2026-01-26. It was re-enabled on 2026-01-27 and no longer supports login from devices running vulnerable versions. Consequently, customers must upgrade to the latest versions listed below for the FortiCloud SSO authentication to function.FortiManager Cloud, FortiAnalyzer Cloud, FortiGate Cloud are NOT impacted.Setups with Custom IdP for SSO instead of FortiCloud are not impacted (including setups using FortiAuthenticator as the Custom IdP)

A missing authentication for critical function in FortiManager 7.6.0, FortiManager 7.4.0 through 7.4.4, FortiManager 7.2.0 through 7.2.7, FortiManager 7.0.0 through 7.0.12, FortiManager 6.4.0 through 6.4.14, FortiManager 6.2.0 through 6.2.12, Fortinet FortiManager Cloud 7.4.1 through 7.4.4, FortiManager Cloud 7.2.1 through 7.2.7, FortiManager Cloud 7.0.1 through 7.0.12, FortiManager Cloud 6.4.1 through 6.4.7 allows attacker to execute arbitrary code or commands via specially crafted requests.

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 use of externally-controlled format string vulnerability [CWE-134] in FortiAnalyzer, FortiAnalyzer Cloud, FortiManager and FortiManager Cloud fazsvcd daemon may allow a remote privileged attacker with admin profile to execute arbitrary code or commands via specially crafted requests.

A use of potentially Dangerous Function vulnerability [CWE-676] in FortiAnalyzer and FortiManager API may allow an authenticated attacker to cause a system hang via multiple specially crafted HTTP requests causing crashes. This happens if internal locks are aligned, which is out of control of the attacker.

An improper restriction of excessive authentication attempts vulnerability [CWE-307] in FortiManager and FortiAnalyzer may allow an attacker to bypass bruteforce protections via exploitation of race conditions.

A use of potentially Dangerous Function vulnerability [CWE-676] in FortiAnalyzer and FortiManager API may allow an authenticated attacker to cause a system hang via multiple specially crafted HTTP requests causing crashes. This happens if internal locks are aligned, which is out of control of the attacker.

An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in FortiAnalyzer, FortiAnalyzer Cloud, FortiManager and FortiManager Cloud may allow a privileged attacker to delete files from the underlying filesystem via crafted CLI requests.

An improper neutralization of special elements used in an SQL command ('SQL injection') [CWE-89] in FortiAnalyzer, FortiAnalyzer Cloud, FortiManager and FortiManager Cloud may allow an authenticated privileged attacker to execute unauthorized code or commands via crafted requests.

An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in FortiAnalyzer, FortiAnalyzer Cloud, FortiManager and FortiManager Cloud may allow a privileged attacker to delete files from the underlying filesystem via crafted CLI requests.

An authentication bypass using an alternate path or channel vulnerability [CWE-288] in FortiManager and FortiAnalyzer multifactor authentication may allow an attacker with knowledge of the admins password to bypass multifactor authentication checks via submitting multiple crafted requests.

A hidden functionality vulnerability in Fortinet FortiAnalyzer 7.6.0 through 7.6.3, FortiAnalyzer 7.4.0 through 7.4.7, FortiAnalyzer 7.2.0 through 7.2.10, FortiAnalyzer 7.0.0 through 7.0.14, FortiAnalyzer 6.4 all versions, FortiAnalyzer Cloud 7.6.2, FortiAnalyzer Cloud 7.4.1 through 7.4.7, FortiAnalyzer Cloud 7.2.1 through 7.2.10, FortiAnalyzer Cloud 7.0.1 through 7.0.14, FortiAnalyzer Cloud 6.4 all versions, FortiManager 7.6.0 through 7.6.3, FortiManager 7.4.0 through 7.4.7, FortiManager 7.2.0 through 7.2.10, FortiManager 7.0.0 through 7.0.14, FortiManager 6.4 all versions, FortiManager Cloud 7.6.2 through 7.6.3, FortiManager Cloud 7.4.1 through 7.4.7, FortiManager Cloud 7.2.1 through 7.2.10, FortiManager Cloud 7.0.1 through 7.0.14, FortiManager Cloud 6.4 all versions may allow a remote authenticated read-only admin with CLI access to escalate their privilege via use of a hidden command.

A Stack-based Buffer Overflow vulnerability [CWE-121] in FortiManager fgtupdates service may allow a remote unauthenticated attacker to execute unauthorized commands via crafted requests, if the service is enabled. The success of the attack depends on the ability to bypass the stack protection mechanisms.

A improper certificate validation vulnerability in Fortinet FortiAnalyzer 7.6.0 through 7.6.4, FortiAnalyzer 7.4.0 through 7.4.8, FortiAnalyzer 7.2 all versions, FortiAnalyzer 7.0 all versions, FortiAnalyzer 6.4 all versions, FortiManager 7.6.0 through 7.6.4, FortiManager 7.4.0 through 7.4.8, FortiManager 7.2 all versions, FortiManager 7.0 all versions, FortiManager 6.4 all versions may allow a remote unauthenticated attacker to view confidential information via a man in the middle [MiTM] attack.

An Inclusion of Undocumented Features [CWE-1242] in FortiManager and FortiAnalyzer CLI may allow a remote authenticated read-only admin with CLI access to escalate their privilege via use of a hidden command.

An authentication bypass using an alternate path or channel vulnerability [CWE-288] in FortiManager and FortiAnalyzer multifactor authentication may allow an attacker with knowledge of the admins password to bypass multifactor authentication checks via submitting multiple crafted requests.

An improper restriction of excessive authentication attempts vulnerability [CWE-307] in FortiManager and FortiAnalyzer may allow an attacker to bypass bruteforce protections via exploitation of race conditions.

An improper certificate validation [CWE-295] vulnerability in the FortiManager GUI may allow a remote unauthenticated attacker to view confidential information via a man in the middle [MiTM] attack.

A Stack-based Buffer Overflow vulnerability [CWE-121] in FortiManager fgtupdates service may allow a remote unauthenticated attacker to execute unauthorized commands via crafted requests, if the service is enabled. The success of the attack depends on the ability to bypass the stack protection mechanisms.