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Fencer Vulns
medium 6.9

CVE-2026-56405 json

libexpat before 2.8.2 has an integer overflow in getAttributeId.

published 2026-06-21 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-38182 , JLSEC-2026-1229

cvss
6.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

libexpat before 2.8.2 has an integer overflow in getAttributeId.

Patch / fix

  • julia Expat_jll 2.8.2+0
  • libexpat project libexpat 2.8.2
  • expat Debian 12 2.5.0-1+deb12u3
  • expat Debian 13 2.8.2-1~deb13u1
  • expat Debian 14 2.8.2-1

debian advisories DEBIAN-CVE-2026-56405

  • expat Ubuntu 22.04 LTS 2.4.7-1ubuntu0.8
  • expat Ubuntu 24.04 LTS 2.6.1-2ubuntu0.5
  • expat Ubuntu 26.04 LTS 2.7.4-1ubuntu0.1
  • expat Ubuntu Pro 14.04 LTS 2.1.0-4ubuntu1.4+esm12
  • expat Ubuntu Pro 16.04 LTS 2.1.0-7ubuntu0.16.04.5+esm13
  • expat Ubuntu Pro 18.04 LTS 2.2.5-3ubuntu0.9+esm4
  • expat Ubuntu Pro 20.04 LTS 2.2.9-1ubuntu0.8+esm2
  • libxmltok Ubuntu Pro 16.04 LTS 1.2-3ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-56405

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

  • expat SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.8.5-160000.1.1
  • expat Linux Micro 6.1 2.8.5-slfo.1.1_1.1
  • MozillaFirefox SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 153.5.0-150400.157.16.1
  • MozillaFirefox SLES for SAP applications 16.0, SLES 16.0 153.5.0-160000.1.1
  • MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7 153.5.0-150400.13.9.1
  • expat SLE Module for Basesystem 15 SP7 2.8.5-150700.3.15.1
  • expat Linux Micro 6.0 2.8.5-159998.1.1
  • expat SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +10 more 2.8.5-150400.3.40.1

suse advisories SUSE-SU-2026:24460-1SUSE-SU-2026:24469-1SUSE-SU-2026:24554-1SUSE-SU-2026:4834-1SUSE-SU-2026:4806-1SUSE-SU-2026:24260-1

  • expat openSUSE Leap 16.0 2.8.5-160000.1.1
  • MozillaFirefox openSUSE Leap 16.0 153.5.0-160000.1.1
  • expat openSUSE Leap 16.0 2.8.4-160000.1.1
  • expat openSUSE Tumbleweed 2.8.2-1.1

opensuse advisories openSUSE-SU-2026:22177-1openSUSE-SU-2026:22139-1openSUSE-SU-2026:21945-1openSUSE-SU-2026:11584-1

  • expat Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 2.8.2-r0

alpine advisories ALPINE-CVE-2026-56405

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

  • expat Azure Linux 3.0 2.8.2-1

azure linux advisories AZL-90228

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-2026-56405 updated cvss 4.9

libexpat: libexpat: Information disclosure and arbitrary code execution via integer overflow

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/lightspeed-chatbot-rhel9, ansible-automation-platform-27/lightspeed-chatbot-rhel9 Red Hat Enterprise Linux 6 expat, compat-expat1 Red Hat Enterprise Linux 7 expat Red Hat Enterprise Linux 8 expat, mingw-expat, mingw32-expat, mingw64-expat Red Hat Enterprise Linux 9 expat
    +3 more products
    Red Hat Enterprise Linux 10 expat Red Hat JBoss Core Services libexpat-2.dll Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-llama-stack-core-rhel9, rhoai/odh-trustyai-garak-lls-provider-dsp-rhel9
    affected: workaround, no fix available “Fix deferred”

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
total
Assessed
4 mo ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.9 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
NVD 3.1 6.9 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
OSV 3.1 6.9 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
julia Expat_jll
<2.8.2+0
2.8.2+0

Affected products

  • libexpat project libexpat

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound

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.