High [CVE-2026-20214] Denial of Service via crafted FSG file parsing
This high-severity Red Hat Linux advisory covers CVE-2026-20214.
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Summary
A vulnerability in the FSG 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 FSG 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 portable executable content compressed with FSG 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. A flaw was found in ClamAV.
An unauthenticated, remote attacker could exploit a vulnerability in the FSG file format parser by submitting a specially crafted file for scanning. This improper handling of FSG files can lead to an out-of-bounds buffer write, causing memory corruption.
This can lead to memory corruption and terminate the ClamAV scanning process, impacting services relying on ClamAV for content inspection. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-787.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
Mitigation checklist
- To reduce the attack surface, restrict network access to the ClamAV daemon (clamd) to trusted clients only. This can be achieved by configuring firewall rules to limit connections to the port clamd listens on. For example, using `firewalld`: `firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<TRUSTED_IP_ADDRESS>" port port="3310" protocol="tcp" accept'` `firewall-cmd --reload` Replace `<TRUSTED_IP_ADDRESS>` with the IP address or network range of trusted clients. This mitigation may impact legitimate scanning operations if not configured correctly. A restart of the `clamd` service may be required for changes to take full effect.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
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