CVE-2026-93990
highpriority · track · 30EPSS 0.004 · 34 %ileDEFREPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.6–8.7
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (11)
Products and version ranges known to be affected.
advisories (3)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-3482expat: Schwachstelle ermöglicht Manipulation von DatenDeutsch2026-09-20csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann eine Schwachstelle in expat ausnutzen, um Daten zu manipulieren.
- CERTFR-2026-AVI-1385Multiples vulnérabilités dans les produits VMwareFrançais2026-10-26vendor · certfrFR
- CERTFR-2026-AVI-1390Multiples vulnérabilités dans Tenable Network MonitorFrançais2026-10-27vendor · certfrFR
sources
Which sources assert this record, and when.
references (6) nvd
External citations — patches, advisories, analysis.
- https://blog.hartwork.org/posts/expat-2-8-5-released/
- https://github.com/libexpat/libexpat
- https://github.com/libexpat/libexpat/commit/ff6e1d7e750bbe245178f51a47a965dc8342861a
- https://github.com/libexpat/libexpat/pull/1282
- https://github.com/libexpat/libexpat/releases/tag/R_2_8_5
- https://www.vulncheck.com/advisories/expat-through-2.8.4-malformed-utf-16-acceptance-via-unchecked-surrogate
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