Input validation error in ClamAV - CVE-2026-20243

Vulnerability identifier: #VU136663

CSH Severity: Medium

CVSS v4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-20243

CWE-ID: CWE-20

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper size handling in the ALZ parser when parsing a malformed ALZ archive. A remote attacker can provide a specially crafted archive to cause a denial of service.

The issue may panic or abort the scanner, and it may also skip expected scan-limit handling.

ClamAV
Secure Endpoint Connector for Mac
Secure Endpoint Connector for Linux
Secure Endpoint Connector for Windows
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
Basesystem Module
openSUSE Leap
Ubuntu
clamav (Ubuntu package)
libclamav12-debuginfo
clamav-docs-html
libclammspack0
libfreshclam4
clamav-debugsource
clamav-milter-debuginfo
clamav
clamav-milter
libclamav12
clamav-debuginfo
clamav-devel
libfreshclam4-debuginfo
libclammspack0-debuginfo

Install security update from vendor's website.

ClamAV - addressed in versions 1.4.5, 1.5.3
clamav (Ubuntu package) - addressed in versions 1.5.3+dfsg-0ubuntu0.22.04.2, 1.5.3+dfsg-0ubuntu0.24.04.1, 1.5.3+dfsg-0ubuntu0.26.04.1
libclamav12-debuginfo - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-docs-html - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
libclammspack0 - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
libfreshclam4 - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-debugsource - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-milter-debuginfo - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-milter - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
libclamav12 - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-debuginfo - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
clamav-devel - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
libfreshclam4-debuginfo - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
libclammspack0-debuginfo - addressed in versions 1.5.3-3.56.1, 1.5.3-150400.13.8.1, 1.5.3-150600.18.28.1
Secure Endpoint Connector for Mac - update to 1.27.2
Secure Endpoint Connector for Linux - update to 1.29.0
Secure Endpoint Connector for Windows - update to 8.6.2

• https://blog.clamav.net/2026/07/clamav-153-and-145-security-patch.html

• Multiple vulnerabilities in ClamAV
• Cisco Secure Endpoint Connector update for ClamAV
• Ubuntu update for clamav
• SUSE update for clamav
• SUSE update for clamav
• SUSE update for clamav