CVE-2021-21826: Att Xmill

Critical severity, CVSS 9.8. EPSS: 1.1% chance of exploitation in the next 30 days.

A heap-based buffer overflow vulnerability exists in the XML Decompression DecodeTreeBlock functionality of AT&T Labs Xmill 0.7. Within `DecodeTreeBlock` which is called during the decompression of an XMI file, a UINT32 is loaded from the file and used as trusted input as the length of a buffer. An attacker can provide a malicious file to trigger this vulnerability.

Affected products

• Att Xmill: version 0.7 only

Published 2021-08-20. Last modified 2026-06-17.