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Fencer Vulns
low 3.1

CVE-2026-59849 json

Libssh: libssh: denial of service via automatic certificate authentication loop

published 2026-07-21 3 mo ago modified 2026-11-06 2 d ago also EUVD-2026-46263

cvss
3.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 0:0.12.0-3.el10_2
  • Red Hat Red Hat Hardened Images 0.12.1-4.hum1
  • libssh Debian 13 0.11.5-0+deb13u1
  • libssh Debian 14 0.12.1-1

debian advisories DEBIAN-CVE-2026-59849

  • libssh Ubuntu 26.04 LTS 0.11.3-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2026-59849

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libssh RHEL 10.2 0.12.0-3.el10_2
  • libssh-config RHEL 10.2 0.12.0-3.el10_2
  • libssh hummingbird 1 0.12.1-4.hum1
  • libssh-config hummingbird 1 0.12.1-4.hum1

red hat advisories RHSA-2026:55855RHSA-2026:42922

  • libssh SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 0.11.5-160000.1.1

suse advisories SUSE-SU-2026:22940-1SUSE-SU-2026:22948-1SUSE-SU-2026:22956-1

  • libssh openSUSE Tumbleweed 0.11.5-1.2
  • libssh openSUSE Leap 16.0 0.11.5-160000.1.1

opensuse advisories openSUSE-SU-2026:11377-1openSUSE-SU-2026:21444-1

  • libssh AlmaLinux 10 0.12.0-3.el10_2
  • libssh-config AlmaLinux 10 0.12.0-3.el10_2

almalinux advisories ALSA-2026:55855

  • libssh Rocky Linux 10 0.12.0-3.el10_2

rocky linux advisories RLSA-2026:55855

  • libssh Alpine 3.24 0.12.1-r0

alpine advisories ALPINE-CVE-2026-59849

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-59849 updated cvss 3.1

libssh: libssh: denial of service via automatic certificate authentication loop

  • Red Hat Enterprise Linux AppStream (v. 10) libssh-devel 0.12.0-3.el10_2, libssh-debuginfo 0.12.0-3.el10_2, libssh-debugsource 0.12.0-3.el10_2 Red Hat Enterprise Linux BaseOS (v. 10) libssh 0.12.0-3.el10_2, libssh-config 0.12.0-3.el10_2
    fixed: vendor fix “Do not connect to untrusted SSH servers and do not use certificates until patched.” RHSA-2026:55855
  • Red Hat Hardened Images libssh 0.12.1-4.hum1, libssh-config 0.12.1-4.hum1
    fixed: vendor fix “Do not connect to untrusted SSH servers and do not use certificates until patched.” RHSA-2026:42922
  • Red Hat Enterprise Linux 8 libssh, libssh-config Red Hat Enterprise Linux 9 libssh, libssh-config
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.