7.5
HIGH
CVSS 3.1
CVE-2026-20243
ClamAV ALZ Archive Processing Denial of Service Vulnerability
Overview
Description
A vulnerability in the ALZ file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition, or possibly other expanded impacts, resulting from memory corruption on an affected device. This vulnerability is due to improper boundary checks for content in ALZ files during scanning, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted file that contains ALZ content to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.
Details
INFO
Published Date :
July 1, 2026, 5:16 p.m.
Last Modified :
Oct. 25, 2026, 5:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework
for assessing the severity of vulnerabilities in software and systems.
We collect and displays CVSS scores from various sources for each CVE.
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
Update ClamAV to a version that addresses memory corruption vulnerabilities in the ALZ parser.
- Update ClamAV to the latest version.
- Apply vendor patches for ClamAV.
- Scan systems for ALZ files.
- Monitor ClamAV process activity.
References
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-20243.
| URL | Resource |
|---|---|
| https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-clamav-88cFYyxR | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-20243 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-20243
weaknesses.
CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call
CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities
CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables
CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow
CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow
CAPEC-42: MIME Conversion MIME Conversion
CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File
CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links
CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags
CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion
CAPEC-67: String Format Overflow in syslog() String Format Overflow in syslog()
CAPEC-92: Forced Integer Overflow Forced Integer Overflow
CAPEC-100: Overflow Buffers Overflow Buffers
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-20243 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-20243 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 25, 2026
Action Type Old Value New Value Added Translation Title: Cisco Secure Endpoint de Cisco, Description: Una vulnerabilidad en el analizador de formato de archivo ALZ de ClamAV podría permitir a un atacante remoto no autenticado causar una condición de DoS, o posiblemente otros impactos expandidos, resultantes de corrupción de memoria en un dispositivo afectado. Esta vulnerabilidad se debe a comprobaciones de límites inadecuadas para el contenido en archivos ALZ durante el escaneo, lo que puede resultar en una escritura de búfer fuera de límites. Un atacante podría explotar esta vulnerabilidad al enviar un archivo manipulado que contiene contenido ALZ para ser escaneado por ClamAV en un dispositivo afectado. Un exploit exitoso podría permitir al atacante causar la terminación del proceso de escaneo de ClamAV, lo que resultaría en una condición de DoS en el software afectado. -
Initial Analysis by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:cisco:secure_endpoint:*:*:*:*:*:linux:*:* versions up to (excluding) 1.29.0 *cpe:2.3:a:cisco:secure_endpoint:*:*:*:*:*:windows:*:* versions up to (excluding) 8.6.2 *cpe:2.3:a:cisco:secure_endpoint:*:*:*:*:*:macos:*:* versions up to (excluding) 1.27.2 Added CPE Configuration OR *cpe:2.3:a:clamav:clamav:*:*:*:*:*:*:*:* versions from (including) 1.5.0 up to (excluding) 1.5.3 *cpe:2.3:a:clamav:clamav:*:*:*:*:*:*:*:* versions from (including) 1.4.0 up to (excluding) 1.4.5 Added Reference Type Cisco Systems, Inc.: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-clamav-88cFYyxR Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 01, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-20243', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-01T17:19:13.065202Z'} -
New CVE Received by [email protected]
Jul. 01, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Cisco', 'product': 'Cisco Secure Endpoint', 'versions': [{'status': 'affected', 'version': '7.0.5'}, {'status': 'affected', 'version': '6.2.19'}, {'status': 'affected', 'version': '7.3.3'}, {'status': 'affected', 'version': '7.2.13'}, {'status': 'affected', 'version': '6.1.5'}, {'status': 'affected', 'version': '6.3.1'}, {'status': 'affected', 'version': '6.2.5'}, {'status': 'affected', 'version': '7.3.5'}, {'status': 'affected', 'version': '6.2.1'}, {'status': 'affected', 'version': '7.2.7'}, {'status': 'affected', 'version': '7.1.1'}, {'status': 'affected', 'version': '6.3.5'}, {'status': 'affected', 'version': '6.2.9'}, {'status': 'affected', 'version': '7.3.1'}, {'status': 'affected', 'version': '6.1.7'}, {'status': 'affected', 'version': '7.2.11'}, {'status': 'affected', 'version': '7.2.3'}, {'status': 'affected', 'version': '7.1.5'}, {'status': 'affected', 'version': '6.3.3'}, {'status': 'affected', 'version': '7.3.9'}, {'status': 'affected', 'version': '6.2.3'}, {'status': 'affected', 'version': '6.1.9'}, {'status': 'affected', 'version': '6.0.9'}, {'status': 'affected', 'version': '7.2.5'}, {'status': 'affected', 'version': '6.0.7'}, {'status': 'affected', 'version': '6.3.7'}, {'status': 'affected', 'version': '1.12.3'}, {'status': 'affected', 'version': '1.8.0'}, {'status': 'affected', 'version': '1.11.1'}, {'status': 'affected', 'version': '1.12.4'}, {'status': 'affected', 'version': '1.10.0'}, {'status': 'affected', 'version': '1.12.0'}, {'status': 'affected', 'version': '1.8.1'}, {'status': 'affected', 'version': '1.10.1'}, {'status': 'affected', 'version': '1.12.1'}, {'status': 'affected', 'version': '1.12.6'}, {'status': 'affected', 'version': '1.14.0'}, {'status': 'affected', 'version': '1.10.2'}, {'status': 'affected', 'version': '1.12.7'}, {'status': 'affected', 'version': '1.12.2'}, {'status': 'affected', 'version': '1.6.0'}, {'status': 'affected', 'version': '1.9.0'}, {'status': 'affected', 'version': '1.11.0'}, {'status': 'affected', 'version': '1.7.0'}, {'status': 'affected', 'version': '1.13.0'}, {'status': 'affected', 'version': '1.8.4'}, {'status': 'affected', 'version': '1.13.1'}, {'status': 'affected', 'version': '1.9.1'}, {'status': 'affected', 'version': '1.12.5'}, {'status': 'affected', 'version': '1.13.2'}, {'status': 'affected', 'version': '8.1.7.21512'}, {'status': 'affected', 'version': '8.1.7'}, {'status': 'affected', 'version': '8.1.5'}, {'status': 'affected', 'version': '8.1.3.21242'}, {'status': 'affected', 'version': '8.1.3'}, {'status': 'affected', 'version': '8.1.5.21322'}, {'status': 'affected', 'version': '8.1.7.21417'}, {'status': 'affected', 'version': '1.14.1'}, {'status': 'affected', 'version': '1.15.1'}, {'status': 'affected', 'version': '1.15.2'}, {'status': 'affected', 'version': '1.15.3'}, {'status': 'affected', 'version': '1.15.4'}, {'status': 'affected', 'version': '1.15.5'}, {'status': 'affected', 'version': '1.15.6'}, {'status': 'affected', 'version': '1.16.0'}, {'status': 'affected', 'version': '1.16.1'}, {'status': 'affected', 'version': '1.16.2'}, {'status': 'affected', 'version': '1.16.3'}, {'status': 'affected', 'version': '1.18.0'}, {'status': 'affected', 'version': '1.18.1'}, {'status': 'affected', 'version': '1.20.0'}, {'status': 'affected', 'version': '1.21.0'}, {'status': 'affected', 'version': '1.21.1'}, {'status': 'affected', 'version': '1.21.2'}, {'status': 'affected', 'version': '1.21.3'}, {'status': 'affected', 'version': '1.22.0'}, {'status': 'affected', 'version': '1.22.1'}, {'status': 'affected', 'version': '1.22.2'}, {'status': 'affected', 'version': '1.22.3'}, {'status': 'affected', 'version': '1.22.4'}, {'status': 'affected', 'version': '1.24.0'}, {'status': 'affected', 'version': '1.24.1'}, {'status': 'affected', 'version': '1.24.2'}, {'status': 'affected', 'version': '1.24.3'}, {'status': 'affected', 'version': '1.24.4'}, {'status': 'affected', 'version': '1.26.0'}, {'status': 'affected', 'version': '1.24.5'}, {'status': 'affected', 'version': '1.26.1'}, {'status': 'affected', 'version': '1.27.0'}, {'status': 'affected', 'version': '1.15.0'}, {'status': 'affected', 'version': '1.17.0'}, {'status': 'affected', 'version': '1.17.1'}, {'status': 'affected', 'version': '1.17.2'}, {'status': 'affected', 'version': '1.19.0'}, {'status': 'affected', 'version': '1.20.1'}, {'status': 'affected', 'version': '1.20.2'}, {'status': 'affected', 'version': '1.20.3'}, {'status': 'affected', 'version': '1.20.4'}, {'status': 'affected', 'version': '1.20.5'}, {'status': 'affected', 'version': '1.20.6'}, {'status': 'affected', 'version': '1.23.0'}, {'status': 'affected', 'version': '1.23.1'}, {'status': 'affected', 'version': '1.20.7'}, {'status': 'affected', 'version': '1.20.8'}, {'status': 'affected', 'version': '1.25.0'}, {'status': 'affected', 'version': '1.25.1'}, {'status': 'affected', 'version': '1.25.2'}, {'status': 'affected', 'version': '1.27.1'}, {'status': 'affected', 'version': '1.27.2'}, {'status': 'affected', 'version': '7.3.13'}, {'status': 'affected', 'version': '7.3.15'}, {'status': 'affected', 'version': '7.4.1'}, {'status': 'affected', 'version': '7.4.1.20425'}, {'status': 'affected', 'version': '7.4.1.20439'}, {'status': 'affected', 'version': '7.4.3'}, {'status': 'affected', 'version': '7.4.3.20679'}, {'status': 'affected', 'version': '7.4.5'}, {'status': 'affected', 'version': '7.5.1.20813'}, {'status': 'affected', 'version': '7.5.1.20833'}, {'status': 'affected', 'version': '7.5.3'}, {'status': 'affected', 'version': '7.5.5'}, {'status': 'affected', 'version': '8.0.1.21160'}, {'status': 'affected', 'version': '8.0.1.21164'}, {'status': 'affected', 'version': '7.5.7'}, {'status': 'affected', 'version': '7.5.9'}, {'status': 'affected', 'version': '7.5.11'}, {'status': 'affected', 'version': '8.1.7.21585'}, {'status': 'affected', 'version': '7.5.13.21586'}, {'status': 'affected', 'version': '7.5.13.21598'}, {'status': 'affected', 'version': '8.2.1.21612'}, {'status': 'affected', 'version': '8.2.1.21650'}, {'status': 'affected', 'version': '7.5.15.21611'}, {'status': 'affected', 'version': '7.5.17.21680'}, {'status': 'affected', 'version': '8.2.3.30119'}, {'status': 'affected', 'version': '8.2.4.30130'}, {'status': 'affected', 'version': '8.4.0'}, {'status': 'affected', 'version': '7.5.19'}, {'status': 'affected', 'version': '8.4.1.30298'}, {'status': 'affected', 'version': '8.4.2.30317'}, {'status': 'affected', 'version': '8.4.1.30307'}, {'status': 'affected', 'version': '7.5.20'}, {'status': 'affected', 'version': '8.4.3'}, {'status': 'affected', 'version': '8.4.4.30419'}, {'status': 'affected', 'version': '8.4.4.30467'}, {'status': 'affected', 'version': '7.5.21.21732'}, {'status': 'affected', 'version': '8.4.5.30483'}], 'defaultStatus': 'unknown'}] Added Description A vulnerability in the ALZ file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition, or possibly other expanded impacts, resulting from memory corruption on an affected device. This vulnerability is due to improper boundary checks for content in ALZ files during scanning, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted file that contains ALZ content to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-120 Added Reference https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-clamav-88cFYyxR
EPSS is a daily estimate of the probability of exploitation activity
being observed over the next 30 days. Following chart shows the EPSS
score history of the vulnerability.