{"id":"CVE-2026-118370","state":"PUBLISHED","title":"libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes","description":"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 with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.","publishedAt":"2026-10-28T02:03:19.447Z","updatedAt":"2026-10-28T02:03:19.447Z","severity":{"score":8.2,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["libexpat libexpat"],"affected":[{"vendor":"libexpat","product":"libexpat","packageURL":"pkg:github/libexpat/libexpat","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"2.9.0","versionType":"semver"}],"repo":"https://github.com/libexpat/libexpat"}],"references":["https://github.com/libexpat/libexpat/pull/1450","https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae","https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c","https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140","https://github.com/libexpat/libexpat","https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes"],"weaknesses":["CWE-190"],"ingestedAt":"2026-10-29T20:10:52.580Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/118xxx/CVE-2026-118370.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-118370","state":"PUBLISHED","datePublished":"2026-10-28T02:03:19.447Z","dateUpdated":"2026-10-28T02:03:19.447Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-10-28T01:19:19.454Z"},"containers":{"cna":{"title":"libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes","descriptions":[{"lang":"en","value":"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 with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory."}],"affected":[{"vendor":"libexpat","product":"libexpat","packageURL":"pkg:github/libexpat/libexpat","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"2.9.0","versionType":"semver"}],"repo":"https://github.com/libexpat/libexpat"}],"references":[{"url":"https://github.com/libexpat/libexpat/pull/1450","tags":["patch","issue-tracking"]},{"url":"https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae","tags":["patch"]},{"url":"https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c","tags":["patch"]},{"url":"https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140","tags":["technical-description"]},{"url":"https://github.com/libexpat/libexpat","tags":["product"]},{"url":"https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes","name":"VulnCheck Advisory: libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","attackVector":"NETWORK","attackComplexity":"HIGH","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.2,"baseSeverity":"HIGH"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","baseScore":5.9,"baseSeverity":"MEDIUM"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-190","lang":"en","description":"Integer Overflow or Wraparound","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-10-28T02:03:19.447Z"},"datePublic":"2026-10-27T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*","versionEndIncluding":"2.9.0"}]}]}],"credits":[{"lang":"en","value":"Mirko Swillus","type":"finder"},{"lang":"en","value":"Sebastian Pipping","type":"remediation developer"}],"x_generator":{"engine":"vulncheck-endgame"}}}}}