CVE-2026-59843

Libssh: libssh: denial of service via zero advertised channel packet size

State: Published
Severity: 6.5 Medium
Published: Jul 21, 2026
Updated: Sep 1, 2026
Reserved: Jul 7, 2026

Description

A flaw was found in libssh. A remote authenticated peer can advertise a zero maximum packet size in SSH_MSG_CHANNEL_OPEN, causing later channel writes to loop indefinitely and consume CPU, leading to denial of service.

Scores

CVSS	Score	Vector	Source
3.1	6.5 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H	redhat

Weaknesses

CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
CWE-400 Uncontrolled Resource Consumption

Affected Products

Product	Versions
Red Hat Enterprise Linux 10Red Hat	0:0.12.0-3.el10_2 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:0.9.6-17.el8_10 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:0.9.6-17.el8_10 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:0.10.4-19.el9_8 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:0.10.4-19.el9_8 and laterNot affected
Red Hat Hardened ImagesRed Hat	0.12.1-4.hum1 and laterNot affected

References

RHSA-2026:42922vendor-advisory
RHSA-2026:55855vendor-advisory
RHSA-2026:62217vendor-advisory
RHSA-2026:62218vendor-advisory
https://access.redhat.com/security/cve/CVE-2026-59843vdb-entry
RHBZ#2498176issue-tracking

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