Within the storm of AI-assisted reports, we are pleased to announce another libssh releases, bringing mostly security relevant fixes for both new features and code that was used for years.
A big thank you to all the security researchers who responsibly reported the issues to us, as well as to all the contributors who made this release possible!
For those new to libssh, we recommend checking out our getting started tutorial. If you have any questions, feel free to join our mailing list or visit our Matrix channel.
You can download libssh-0.12.1 here and libssh-0.11.5 in here.
ChangeLog for libssh 0.12.1:
Security:
- CVE-2026-15370: Stack buffer overflow in SFTP server longname construction
- CVE-2026-59842: Information disclosure via short GSSAPI Curve25519 public key
- CVE-2026-59843: Denial of service via zero advertised channel packet size
- CVE-2026-59844: Denial of service via oversized SFTP read length
- CVE-2026-59845: Denial of service via unchecked ProxyCommand fork() failure
- CVE-2026-59846: Information disclosure via ProxyCommand %r username expansion
- CVE-2026-59847: Integrity downgrade via OpenSSL AES-GCM tag verification
- CVE-2026-59848: Denial of service via SFTP responses with unknown request IDs
- CVE-2026-59849: Denial of service via automatic certificate authentication loop
- CVE-2026-59850: Use-after-free via data callbacks on closed channels
- CVE-2026-59851: Authentication bypass via missing GSSAPI principal check
- Zero-initialize every ssh_string
Compatibility:
- Fix compatibility with C23 / gcc16
- Allow hybrid ML-KEM key exchange in FIPS mode
Bugfixes:
- Fix multiple memory leaks, null checks, and error checks
- Fix parameter size mismatch in mlkem768x25519-sha256
- Fix client SFTP messages being ignored if sent at high rate
- Validate peer public key in DH key exchange
- Fix ambiguous error reporting of sftp_init
- Fix hidden integer underflow in socket packet callback
- Avoid remote window overflow
- Fix socket data callback return value on rekey failure
- Avoid off-by-one overflow during kbdint authentication
- Avoid logging uninitialized sequence numbers
- Avoid double conversion of SFTP version number
- Send correct SFTP server version number
- Avoid handling repeated SFTP INIT messages
- Harmonize return values from SFTP server callbacks
ChangeLog for libssh 0.11.5
Security:
- CVE-2026-15370: Stack buffer overflow in SFTP server longname construction
- CVE-2026-59843: Denial of service via zero advertised channel packet size
- CVE-2026-59844: Denial of service via oversized SFTP read length
- CVE-2026-59845: Denial of service via unchecked ProxyCommand fork() failure
- CVE-2026-59846: Information disclosure via ProxyCommand %r username expansion
- CVE-2026-59847: Integrity downgrade via OpenSSL AES-GCM tag verification
- CVE-2026-59848: Denial of service via SFTP responses with unknown request IDs
- CVE-2026-59849: Denial of service via automatic certificate authentication loop
- CVE-2026-59850: Use-after-free via data callbacks on closed channels
- Zero-initialize every ssh_string
Compatibility:
- Fix compatibility with C23 / gcc16
Bugfixes:
- Fix multiple memory leaks, null checks, and error checks
- Validate peer public key in DH key exchange
- Avoid remote window overflow
- Avoid off-by-one overflow during kbdint authentication
- Avoid logging uninitialized sequence numbers
- Avoid double conversion of SFTP version number
- Send correct SFTP server version number
- Avoid handling repeated SFTP INIT messages
- Harmonize return values from SFTP server callbacks