CVE-2023-20052

What it actually does

XML external entity injection in the DMG file parser enables the ClamAV scanning process to resolve external entities and leak bytes from any locally readable file.

Why it matters to the business

Attackers may obtain sensitive configuration, credential, or data files accessible to the scanner, raising the chance of targeted data theft or follow-on compromise with moderate urgency given the 1325 days since disclosure and low EPSS trend.

How an attack unfolds

An attacker prepares a DMG archive embedding a malicious XML document that references an external entity pointing to a target file on the system, then delivers the file to any ClamAV instance performing scans; the parser substitutes the entity and returns the leaked content to the attacker.

How to fix it

Upgrade ClamAV to a version newer than 1.0.0, 0.105.1, or 0.103.7; apply the exact fixed packages listed for each affected distribution (mediawiki 1:1.19.2-1 on Debian 11/12/13 and 1:1.19.14+dfsg-1 on Ubuntu 14.04 LTS) and restart all scanning services.

How to confirm the fix worked

Confirm the installed ClamAV version is newer than the vulnerable releases, run a test DMG containing a benign XXE payload and verify no external content is leaked, and review release notes or package changelogs for the XXE parser fix.

Typical attack path

1. Create a DMG container containing an XXE payload in its XML metadata
2. Submit the crafted DMG to a ClamAV scanner over the network or via file upload
3. ClamAV opens the DMG and enables XML entity substitution during parsing
4. Entity expansion reads bytes from an arbitrary file readable by the ClamAV process
5. Leaked bytes are returned in the scan response or error output

How to detect it

Review ClamAV process logs and file-access audit trails for unexpected reads of configuration or credential files during DMG scans; correlate scan start times with unusual outbound or error responses containing file contents.

What your security team should do

• Prioritize patching all ClamAV instances within the next maintenance window
• Restrict file-system permissions of the ClamAV process to the minimum required directories
• Disable DMG scanning if the feature is not needed until patches are applied
• Add outbound network controls that prevent the scanner from fetching external entities