CVE-2026-93990 (GCVE-0-2026-93990)

Vulnerability from cvelistv5 – Published: 2026-09-19 22:58 – Updated: 2026-09-28 16:11
VLAI
Title
Expat before 2.8.5 Malformed UTF-16 Acceptance via Unchecked Surrogate
Summary
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.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-21 15:10 UTC
CWE
  • CWE-176 - Improper Handling of Unicode Encoding
Assigner
References
Impacted products
Vendor Product Version CPE status
libexpat libexpat Affected: 0 , < 2.8.5 (semver)
Unaffected: 2.8.5 (semver)
    cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-09-18 00:00
Credits
Kartik Kenchi (netliomax25-code)
Show details on NVD website
To clipboard 

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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.