MajorCritical vulnerability

CVE-2026-93990 (CVSS 8.7)

NVD · officialPublished Sep 19, 2026Risk 37/100EPSS 0.3%

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.

Technical details

CVSS

8.7

AV:NetworkAC:LowPR:NoneUI:None

Evidence and sources

This record is attributed to NVD. Exploitation status and remediation guidance are kept separate from the vulnerability's technical severity.

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