{"id":"CVE-2026-93990","title":"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","summary":"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 c…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","cwe":["CWE-176","CWE-91"],"vendor":"libexpat","product":"libexpat","affected":["libexpat <= 2.8.4"],"published":"2026-09-19","updated":"2026-09-22","sourceUpdated":"2026-09-22T20:25:55.870","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-93990","references":[{"url":"https://github.com/libexpat/libexpat","label":"disclosure@vulncheck.com"},{"url":"https://github.com/libexpat/libexpat/commit/ff6e1d7e750bbe245178f51a47a965dc8342861a","label":"disclosure@vulncheck.com"},{"url":"https://github.com/libexpat/libexpat/pull/1282","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/expat-through-2.8.4-malformed-utf-16-acceptance-via-unchecked-surrogate","label":"disclosure@vulncheck.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-93990.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-93990"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2538967"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-93990"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93990"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00347,"epssPercentile":0.28328,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-21T15:10:43.564847Z"},"ingestedAt":"2026-09-19T23:10:34.247Z","slug":"CVE-2026-93990","body":"## Overview\n\nExpat 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat OpenShift Container Platform 4 · updated 2026-09-22 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-93990.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}