CVE-2026-59843

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

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Severity

Moderate

Red Hat Product Security

6.5

CVSS 3.1

Review impact separately from score.

Published · July 21, 2026

Updated · September 2, 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.

CVSS score applicability

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation

No workaround available.

CVSS / CWE

CVSS 3.1 · 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')