Vulnerability record/PUBLISHED/Published Sep 19, 2026 22:58:11 UTC
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 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.
Base score8.7/ 10
SeverityHighCVSS 4.0
Exploitability / impact
CVSS metric breakdown
Base severityHigh
Attack vectorNetworkAV
Attack complexityLowAC
Attack requirementsNoneAT
Privileges requiredNonePR
User interactionNoneUI
Vulnerable system confidentialityNoneVC
Vulnerable system integrityHighVI
Vulnerable system availabilityNoneVA
Subsequent system confidentialityNoneSC
Subsequent system integrityNoneSI
Subsequent system availabilityNoneSA
CVSS vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NCVSS communicates standardized severity and impact characteristics. It does not establish whether a system is exploitable in your specific environment.
Record context
CVE Numbering AuthorityVulnCheck
Last updatedNov 8, 2026 14:09:22 UTC
PublishedSep 19, 2026 22:58:11 UTC
ReservedSep 19, 2026 10:55:49 UTC
Credits
- Kartik Kenchi (netliomax25-code)