CVE-2026-59842

In libssh up to 0.11.3, the functions sftp_extensions_get_name and sftp_extensions_get_data in src/sftp.c (SFTP Extension Name Handler component) can cause an out-of-bounds read when the idx argument is manipulated. The attack may be performed remotely. Upgrading to version 0.11.4 or 0.12.0 resolves the issue (patch 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60).

A NULL pointer dereference was found in libssh during re-keying with algorithm guessing. This issue may allow an authenticated client to cause a denial of service.

Versions of libssh before 0.6.5 have a state validation issue in the handling of SSH_MSG_NEWKEYS and SSH_MSG_KEXDH_REPLY packets, which can lead to system crashes.

Vulnerability in the libssh library on servers with GSSAPIKeyExchange enabled. The gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users.

In the libssh library, if data packets are processed after a channel is closed, channel data callbacks can be invoked after the associated data has already been freed, leading to crashes or possible use-after-free conditions.

A logic error in libssh's automatic certificate-based public key authentication causes libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

Vulnerability in libssh. A malicious SFTP server can send responses for unknown request IDs, causing unbounded memory growth and client-side denial of service.

A flaw in libssh. Incorrect AES-GCM finalization checks in builds using the OpenSSL backend can effectively remove integrity protection, allowing an in-path attacker to modify plaintext on the wire without detection.

A flaw in libssh: a malicious username expanded through %r in ProxyCommand handling can inject shell metacharacters, exposing environment variables and causing unintended shell behavior.

In libssh, when ProxyCommand is used, an unchecked fork() failure can result in storing PID -1. During cleanup, signals may be sent to processes in the caller's process tree, causing local denial of service.