{"id":"CVE-2026-118370","title":"libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes","summary":"libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document…","severity":"medium","cvss":5.9,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cvssSource":"cna","cwe":["CWE-190"],"vendor":"libexpat","product":"libexpat","affected":["libexpat <= 2.9.0"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T02:03:19.447Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-118370","references":[{"url":"https://github.com/libexpat/libexpat/pull/1450"},{"url":"https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae"},{"url":"https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c"},{"url":"https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140"},{"url":"https://github.com/libexpat/libexpat"},{"url":"https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes","label":"VulnCheck Advisory: libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes"}],"tags":["cve.org"],"ingestedAt":"2026-10-28T03:02:57.627Z","slug":"CVE-2026-118370","body":"## Overview\n\nlibexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.\n\n## Affected\n\n- `libexpat <= 2.9.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":32,"depthScoreParts":{"impact":32.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}