Always-Incorrect Control Flow Implementation in libssh - CVE-2026-59849
Published: July 27, 2026
Vulnerability identifier: #VU139532
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-59849
CWE-ID: CWE-670
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: libssh
Affected software:
libssh
libssh
Detailed vulnerability description
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to improper state management in ssh_userauth_publickey_auto() when handling automatic public key authentication with configured certificates. A remote user can reject a configured certificate or trigger error handling for a missing configured certificate to cause a denial of service.
Only the client side is affected, and exploitation requires a specific configuration in which certificate-based automatic authentication is used; the infinite loop occurs when the server does not enforce an authentication limit.
How to mitigate CVE-2026-59849
Install security update from vendor's website.