What’s Vulnerable › Vulnerabilities

CVE-2026-59843: Libssh: libssh: denial of service via zero advertised channel packet size

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-21 · updated 2026-09-01
• Weakness: CWE-835

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.

Affected products

• libssh: all versions
• Red Hat Enterprise Linux: 8.0, 9.0, 10.0
• RedHat Hardened Images: all versions

References

• https://access.redhat.com/errata/RHSA-2026:42922
• https://access.redhat.com/errata/RHSA-2026:55855
• https://access.redhat.com/errata/RHSA-2026:62217
• https://access.redhat.com/errata/RHSA-2026:62218
• https://access.redhat.com/security/cve/CVE-2026-59843
• https://bugzilla.redhat.com/show_bug.cgi?id=2498176

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