A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.

A Stack-based Buffer Overflow vulnerability [CWE-121] in FortiOS explicit proxy may allow an unauthenticated attacker who can bypass stack protection and ASLR to execute arbitrary code or commands in the context of the WAD daemon via crafted sockets, only if the explicit proxy is configured with Kerberos authentication and SOCKS enabled.

A incomplete list of disallowed inputs vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.2, FortiWeb 7.6.0 through 7.6.5, FortiWeb 7.4 all versions, FortiWeb 7.2 all versions, FortiWeb 7.0 all versions may allow attacker to improper access control via <insert attack vector here>

A Improper Access Control in Fortinet FortiOS 6.0.2, 5.6.7 and before, FortiADC 6.1.0, 6.0.0 to 6.0.1, 5.4.0 to 5.4.4 allows attacker to obtain the LDAP server login credentials configured in FortiGate via pointing a LDAP server connectivity test request to a rogue LDAP server instead of the configured one.

A allocation of resources without limits or throttling vulnerability in Fortinet FortiOS 7.6.0 through 7.6.6, FortiOS 7.4 all versions, FortiOS 7.2 all versions may allow attacker to denial of service via <insert attack vector here>

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.

CVE-2026-49975Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's modhttp leads to denial of service via malicious HTTP requests. This issue affects Apache HTTP Server: from 2.4.17 through 2.4.67.

An Allocation of Resources Without Limits or Throttling vulnerability [CWE-770] in FortiOS may allow an unauthenticated attacker to perform a slow HTTP DoS attack on the web interface via crafted HTTP requests.

A Stack-based Buffer Overflow vulnerability [CWE-121] in FortiOS explicit proxy may allow an unauthenticated attacker who can bypass stack protection and ASLR to execute arbitrary code or commands in the context of the WAD daemon via crafted sockets, only if the explicit proxy is configured with Kerberos authentication and SOCKS enabled.

A improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiOS 7.6.0 through 7.6.6, FortiOS 7.4.0 through 7.4.9, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4 all versions, FortiPAM 1.8.0, FortiPAM 1.7.0 through 1.7.2, FortiPAM 1.6 all versions, FortiPAM 1.5 all versions, FortiPAM 1.4 all versions, FortiPAM 1.3 all versions, FortiPAM 1.2 all versions, FortiPAM 1.1 all versions, FortiPAM 1.0 all versions, FortiProxy 7.6.0 through 7.6.5, FortiProxy 7.4 through 7.4.13, FortiProxy 7.2 all versions, FortiProxy 7.0 all versions may allow attacker to execute unauthorized code or commands via <insert attack vector here>

A buffer over-read vulnerability [CWE-126] in FortiOS, FortiProxy, and FortiSASE may allow an authenticated remote attacker to return a portion of device memory in the redirect response via submitting a specially crafted request.

A Stack-based Buffer Overflow vulnerability [CWE-121] in FortiOS, FortiProxy and FortiPAM may allow a privileged authenticated attacker who can bypass stack protection and ASLR to execute arbitrary code or commands via crafted HTTP requests.

An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability [CWE-79] in FortiOS, FortiProxy, FortiPAM and FortiSwitch-Manager Agentless SSL-VPN may allow an authenticated remote user to execute code or commands via crafted requests.

An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability [CWE-113] in FortiOS and FortiProxy may allow an attacker in possession of a valid web filter override token to inject arbitrary headers via tricking a user into clicking on a crafted link.

An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability [CWE-113] in FortiOS and FortiProxy captive portal may allow an attacker able to intercept and modify a user's authentication request to inject arbitrary headers via crafted HTTP requests.

A buffer over-read vulnerability [CWE-126] in FortiOS, FortiProxy, and FortiSASE may allow an authenticated remote attacker to return a portion of device memory in the redirect response via submitting a specially crafted request.

An Internal Asset Exposed to Unsafe Debug Access Level or State vulnerability [CWE-1244] in FortiOS and FortiProxy may allow an authenticated admin to execute lua scripts via crafted CLI commands.

An Unchecked Return Value vulnerability [CWE-252] in Fortinet FortiOS version 7.6.0 through 7.6.3 and before 7.4.8 API allows an authenticated user to cause a Null Pointer Dereference, crashing the http daemon via a specialy crafted request.

An Improper Privilege Management vulnerability [CWE-269] in FortiOS, FortiProxy and FortiPAM may allow an authenticated administrator to bypass the trusted host policy via crafted CLI command.

An Improper Neutralization of Input During Web Page Generation and URL Redirection to Untrusted Site vulnerabilities [CWE-79, CWE-601] in FortiOS, FortiProxy and FortiSASE may allow an unauthenticated attacker to perform a reflected cross site scripting (XSS) or an open redirect attack via crafted HTTP requests.

A insertion of sensitive information into log file vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4 all versions, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4 all versions, FortiProxy 7.6.0 through 7.6.3, FortiProxy 7.4.0 through 7.4.13, FortiProxy 7.2 all versions, FortiProxy 7.0 all versions may allow attacker to information disclosure via <insert attack vector here>

An Improper Neutralization of Input During Web Page Generation and URL Redirection to Untrusted Site vulnerabilities [CWE-79, CWE-601] in FortiOS, FortiProxy and FortiSASE may allow an unauthenticated attacker to perform a reflected cross site scripting (XSS) or an open redirect attack via crafted HTTP requests.

An Exposure of Sensitive Information to an Unauthorized Actor vulnerability [CWE-200] in FortiOS SSL-VPN web-mode may allow an authenticated user to access full SSL-VPN settings via crafted URL.

An Integer Overflow or Wraparound vulnerability [CWE-190] in FortiOS version 7.6.2 and below, version 7.4.7 and below, version 7.2.10 and below, 7.2 all versions, 6.4 all versions, FortiProxy version 7.6.2 and below, version 7.4.3 and below, 7.2 all versions, 7.0 all versions, 2.0 all versions and FortiPAM version 1.5.0, version 1.4.2 and below, 1.3 all versions, 1.2 all versions, 1.1 all versions, 1.0 all versions SSL-VPN RDP and VNC bookmarks may allow an authenticated user to affect the device SSL-VPN availability via crafted requests.

An Improper Certificate Validation vulnerability [CWE-295] in FortiOS may allow an EAP verified remote user to connect from FortiClient via revoked certificate.

An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] in FortiOS 7.4.0 through 7.4.7, 7.2.0 through 7.2.11, 7.0.6 and above; and FortiProxy 7.6.0 through 7.6.2, 7.4.0 through 7.4.8, 7.2 all versions, 7.0.5 and above may allow an authenticated attacker to elevate their privileges via triggering a malicious Webhook action in the Automation Stitch component.

An Improperly Implemented Security Check for Standard vulnerability [CWE-358] in FortiOS and FortiProxy may allow a remote unauthenticated user to bypass the DNS filter via Apple devices.

A out-of-bounds write in Fortinet FortiOS versions 7.6.0, 7.4.0 through 7.4.6, 7.2.0 through 7.2.10, 7.0.0 through 7.0.16, 6.4.0 through 6.4.15 allows attacker to trigger a denial of service via specially crafted packets.

An Insufficient Session Expiration vulnerability [CWE-613] in FortiOS SSL-VPN may allow an attacker in possession of a cookie used to log in the SSL-VPN portal to log in again, although the session has expired or was logged out.