CVE-2026-59845
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
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.
Risk Assessment
An attacker can cause signals to be sent to random processes, potentially disrupting system or other applications.
Recommendation
Update libssh to a version containing the fix. Avoid using ProxyCommand with untrusted configurations.
Other vulnerabilities in libssh
See all- CVE-2026-3731Medium
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).
- CVE-2023-1667Medium
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.
- CVE-2015-3146High
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.
- CVE-2026-59851High
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.
- CVE-2026-59850Medium
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.
- CVE-2026-59849Low
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.
- CVE-2026-59848Medium
Vulnerability in libssh. A malicious SFTP server can send responses for unknown request IDs, causing unbounded memory growth and client-side denial of service.
- CVE-2026-59847Medium
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.
- CVE-2026-59846Low
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.
- CVE-2026-59844Medium
A flaw in libssh: a remote authenticated client can issue SFTP_READ requests with an arbitrarily large length, causing the SFTP server to allocate excessive memory and potentially exhaust it.
Original NVD description (English source)
A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS