CVE-2026-20347: ClamAV Mach-O File Format Processing Memory Corruption Vulnerability

highCVSS 7.5CVE-2026-20347

CSIRTS triage

vendor: ClamAV product: ClamAV Memory corruption

What: Memory corruption occurs when processing malformed Mach-O file formats.
Who is affected: All ClamAV deployments using Mach-O file scanning.
Urgency: High severity (CVSS 7.5) but not currently exploited; patch promptly.
Action: Upgrade ClamAV to the patched version addressing CVE-2026-20347.

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

⚡ Watch ClamAV

Get an email when a new ClamAV advisory drops — max one per day, one-click unsubscribe.

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-2026-20347

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-2026-203470.33% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 26% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-20347	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-2026-20347: A vulnerability in the Mach-O file format parser of ClamAV could allow an unauthenticated, rem…nvd

Recent advisories for ClamAV Mach-O 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-2026-20347: A vulnerability in the Mach-O file format parser of ClamAV could allow an unauthenticated, rem…nvd · 2026-08-07