CVE-2026-20337: ClamAV ZIP File Format Processing Memory Corruption Vulnerability

highCVSS 7.5CVE-2026-20337

CSIRTS triage

vendor: ClamAV product: ClamAV Memory corruption

What: Memory corruption occurs when processing malformed ZIP file formats.
Who is affected: All ClamAV deployments using ZIP file scanning.
Urgency: High severity (CVSS 7.5) but not currently exploited; patch promptly.
Action: Upgrade ClamAV to the patched version addressing CVE-2026-20337.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20337

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-203370.36% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 29% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-20337	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highClamAV Vulnerabilities Affecting Cisco Products: August 2026cisco-psirt
unknownexploitedCisco Products Multiple Vulnerabilitieshkcert
high[NEW] [high] ClamAV: Multiple vulnerabilities allow Denial of Service and disclosure of informationcert-bund
unknownexploitedMultiple vulnerabilities in ClamAV (August 10, 2026)cert-fr-avis
highCVE-2026-20337: A vulnerability in the zip archive parser of ClamAV could allow an unauthenticated, remote att…nvd

Recent advisories for ClamAV ZIP File

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-20338: ClamAV ZIP File Format Processing Memory Corruption Vulnerabilitymsrc · 2026-08-11