CVE WatchSep 28, 2026

CVE-2026-93990

Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequenc

CVSS

7.5

High

EPSS

0.4%

p33

KEV

—

Exploit Today

0-100

Published: Sep 19, 2026 · Last modified: Sep 28, 2026 · CWE-176

EPSS · 30d

0.3%EPSS · 30 days0.5%

2026-09-212026-10-19

Technical description

Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following code unit, causing Expat to pass unpaired surrogates to applications built with XML_UNICODE and to silently replace input characters in other builds.

Official references

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