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Fencer Vulns
low 3.1

CVE-2025-8277 json

Libssh: memory exhaustion via repeated key exchange in libssh

published 2025-09-09 13 mo ago modified 2026-11-06 2 d ago also EUVD-2025-27246

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 37%
public exploits
0
none known

Summary

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 9 0:0.10.4-18.el9
  • libssh Debian 12 0.10.6-0+deb12u2
  • libssh Debian 13 0.11.2-1+deb13u1
  • libssh Debian 14 0.11.3-1

debian advisories DEBIAN-CVE-2025-8277

  • libssh Ubuntu 22.04 LTS 0.9.6-2ubuntu0.22.04.6
  • libssh Ubuntu 24.04 LTS 0.10.6-2ubuntu0.3
  • libssh Ubuntu 25.10 0.11.2-1ubuntu0.2
  • libssh Ubuntu Pro 18.04 LTS 0.8.0~20170825.94fa1e38-1ubuntu0.7+esm6
  • libssh Ubuntu Pro 20.04 LTS 0.9.3-2ubuntu2.5+esm3

ubuntu advisories UBUNTU-CVE-2025-8277

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 9 0.10.4-18.el9
  • libssh-config RHEL 9 0.10.4-18.el9

red hat advisories RHSA-2026:18683

  • libssh SLE Micro 5.5, SLE Micro 5.4, SLE Micro 5.3 0.9.8-150400.3.12.1
  • libssh SLE Micro 5.2, SLE Micro 5.1 0.9.8-150200.13.12.1
  • libssh Linux Micro 6.1 0.10.6-slfo.1.1_3.1
  • libssh Linux Micro 6.0 0.10.6-3.1
  • libssh SLE Module for Basesystem 15 SP7, SLE Module for Basesystem 15 SP6, openSUSE Leap 15.6 0.9.8-150600.11.6.1
  • libssh SLES LTSS Extended Security 12 SP5 0.6.3-12.18.1
  • libssh SLES LTSS Extended Security 12 SP5 0.9.8-3.18.1

suse advisories SUSE-SU-2025:3897-1SUSE-SU-2025:3788-1SUSE-SU-2025:3787-1SUSE-SU-2025:20894-1SUSE-SU-2025:20847-1SUSE-SU-2025:03369-1

  • libssh openSUSE Tumbleweed 0.11.3-1.1

opensuse advisories openSUSE-SU-2025:15545-1

  • libssh AlmaLinux 9 0.10.4-18.el9
  • libssh-config AlmaLinux 9 0.10.4-18.el9

almalinux advisories ALSA-2026:18683

  • libssh Rocky Linux 9 0.10.4-18.el9

rocky linux advisories RLSA-2026:18683

  • libssh CBL-Mariner 2.0 0.10.6-5
  • libssh Azure Linux 3.0 0.10.6-4

azure linux advisories AZL-67092AZL-67095

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2025-8277 updated cvss 3.1

libssh: Memory Exhaustion via Repeated Key Exchange in libssh

  • Red Hat Enterprise Linux 6 libssh2
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 libssh2 Red Hat Enterprise Linux 8 libssh, libssh-config Red Hat Enterprise Linux 10 libssh Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) libssh-devel 0.10.4-18.el9, libssh-debuginfo 0.10.4-18.el9, libssh-debugsource 0.10.4-18.el9 Red Hat Enterprise Linux BaseOS (v. 9) libssh 0.10.4-18.el9, libssh-config 0.10.4-18.el9
    fixed: vendor fix RHSA-2026:18683

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
13 mo ago

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 37% 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

Affected products

  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime

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.