CVE-2021-21828
CVSS v3
9.8
CRITICAL
EPSS Score
1.1 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
A heap-based buffer overflow vulnerability exists in the XML Decompression DecodeTreeBlock functionality of AT&T Labs Xmill 0.7. In the default case of DecodeTreeBlock a label is created via CurPath::AddLabel in order to track the label for later reference. An attacker can provide a malicious file to trigger this vulnerability.
Technical details
- Published
- 2021-08-20
Frequently asked questions
What is CVE-2021-21828?
A heap-based buffer overflow vulnerability exists in the XML Decompression DecodeTreeBlock functionality of AT&T Labs Xmill 0.7. In the default case of DecodeTreeBlock a label is created via CurPath::AddLabel in order to track the label for later reference. An attacker can provide a malicious file to trigger this vulnerability.
Is CVE-2021-21828 actively exploited?
Active exploitation of CVE-2021-21828 has not been confirmed. Its EPSS score was 1.1% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-21828?
CVE-2021-21828 has a CVSS v3 base score of 9.8 (CRITICAL severity).
Is CVE-2021-21828 affecting your environment?
Use isMalicious to check if any of your IPs or domains are associated with this vulnerability's IOCs.
No credit card required · 500 free checks/month · Free API key
Other 2021 vulnerabilities worth triaging
Ranked by exploit probability (EPSS).