Vulnerability Description
Expat through 2.8.4 fails to validate low surrogates following high surrogates in UTF-16 input, allowing malformed UTF-16 sequences to be accepted. Attackers can craft UTF-16 encoded XML with lone high surrogates that consume following code units, hiding markup characters from the parser and enabling XML injection attacks.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/libexpat/libexpat
- https://github.com/libexpat/libexpat/commit/ff6e1d7e750bbe245178f51a47a965dc8342
- https://github.com/libexpat/libexpat/pull/1282
- https://www.vulncheck.com/advisories/expat-through-2.8.4-malformed-utf-16-accept
FAQ
What is CVE-2026-93990?
CVE-2026-93990 is a vulnerability with a CVSS score of 7.5 (HIGH). Expat through 2.8.4 fails to validate low surrogates following high surrogates in UTF-16 input, allowing malformed UTF-16 sequences to be accepted. Attackers can craft UTF-16 encoded XML with lone hig...
How severe is CVE-2026-93990?
CVE-2026-93990 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-93990?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.