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Fencer Intel
medium 5.3

CVE-2026-20031 json

ClamAV CSS Image Parsing Error Handling Denial of Service Vulnerability

published 8mo ago modified 4mo ago also EUVD-2026-9433

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

A vulnerability in the HTML Cascading Style Sheets (CSS) module of ClamAV could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to improper error handling when splitting UTF-8 strings. An attacker could exploit this vulnerability by submitting a crafted HTML file to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to terminate the scanning process.

Patch / fix

  • cisco clam_antivirus 1.4.4-0, 1.5.2-0
  • cisco clamav 1.4.4-0, 1.5.2-0
  • clamav clamav 1.4.4-0, 1.5.2-0
  • clamavs clamav 1.4.4-0, 1.5.2-0
  • clam_anti-virus clamav 1.4.4-0, 1.5.2-0
  • cisco secure_endpoint 1.27.2, 1.28.1, 8.6.0
  • cisco secure_endpoint_private_cloud 4.2.7
  • clamav Debian 12 1.4.6+dfsg-0+deb12u1
  • clamav Debian 14 1.4.4+dfsg-1

debian advisories DEBIAN-CVE-2026-20031

  • clamav Ubuntu 22.04 LTS 1.4.4+dfsg-0ubuntu0.22.04.1
  • clamav Ubuntu 24.04 LTS 1.4.4+dfsg-0ubuntu0.24.04.1
  • clamav Ubuntu 25.10 1.4.4+dfsg-0ubuntu0.25.10.1
  • clamav Ubuntu 26.04 LTS 1.4.4+dfsg-0ubuntu0.26.04.1

ubuntu advisories UBUNTU-CVE-2026-20031

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

  • clamav SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 1.5.2-150400.13.5.1
  • clamav SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Basesystem 15 SP7 +1 more 1.5.2-150600.18.25.1
  • clamav SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 1.5.2-3.53.1

suse advisories SUSE-SU-2026:0906-2SUSE-SU-2026:1325-1SUSE-SU-2026:1324-1

  • clamav openSUSE Leap 16.0 1.5.2-160000.1.1
  • clamav openSUSE Tumbleweed 1.5.2-1.1

opensuse advisories openSUSE-SU-2026:20479-1openSUSE-SU-2026:10325-1

  • clamav Alpine 3.24, Alpine 3.23 1.4.4-r0

alpine advisories ALPINE-CVE-2026-20031

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

Is CVE-2026-20031 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2026-20031 updated cvss 5.3

ClamAV: improper error handling when splitting UTF-8 strings in the HTML Cascading Style Sheets (CSS) module

  • Red Hat All currently supported Red Hat products
    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
yes
Technical impact
partial
Assessed
8mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • Cisco Cisco Secure Endpoint

Classification

Weakness

References

Sources

Fencer Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.