Cisco ClamAV Zip Archive Parser out-of-bounds write

Summaryinfo

A vulnerability marked as critical has been reported in Cisco ClamAV. The affected element is an unknown function of the component Zip Archive Parser. The manipulation leads to out-of-bounds write. This vulnerability is documented as CVE-2026-20337. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Cisco ClamAV (the affected version is unknown) and classified as critical. This issue affects an unknown code of the component Zip Archive Parser. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is integrity, and availability. The summary by CVE is:

A vulnerability in the zip archive parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition on an affected device. This vulnerability is due to improper boundary checks for content in zip files during scanning, which may result in an out-of-bounds write condition. An attacker could exploit this vulnerability by submitting a crafted zip file for scanning. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.

The advisory is shared at sec.cloudapps.cisco.com. The identification of this vulnerability is CVE-2026-20337 since 10/08/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/07/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Anti-Malware Software

Vendor

• Cisco

Name

• ClamAV

License

• free

Website

• Vendor: https://www.cisco.com/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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