Infinite loop in libssh - CVE-2026-59843
Published: July 27, 2026
Vulnerability identifier: #VU139526
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-59843
CWE-ID: CWE-835
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 an infinite loop in channel_write_common() when processing an SSH_MSG_CHANNEL_OPEN request with a maximum packet length of zero. A remote user can send a specially crafted channel open request to cause a denial of service.
Repeating the attack over multiple connections can exhaust CPU resources of the server.
How to mitigate CVE-2026-59843
Install security update from vendor's website.