Multiple vulnerabilities have been discovered in the open-source antivirus scanner ClamAV, caused by flawed processing of input data. A remote, unauthenticated attacker can exploit these flaws to trigger a denial of service or expose sensitive information.
What's going on
ClamAV scans files and emails for malware. Ironically, when processing certain crafted files, the scanner itself can become the target. An attacker sends a specially prepared file, the scanner tries to process it, and a bug causes a crash or leaks information. This is particularly uncomfortable because ClamAV is often deployed as a protective layer for mail servers and other infrastructure.
What to do
Update ClamAV to the latest stable version. The ClamAV project releases updates regularly. On Linux, install the update via your package manager, for example with apt upgrade clamav. If you run ClamAV as a mail gateway filter, verify that everything is working correctly after the update.
Keep your virus signature database up to date as well. An outdated signature set can introduce gaps even when the scanner itself is fully patched.