# CVE-2026-117610: libexpat through 2.9.0 NULL Pointer Dereference via External Entity Subparser Status: published. Published: 2026-10-28. Updated: 2026-11-05. libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the XML_TOK_NONE token from empty input. Attackers who control stream chunking can force an empty non-final first parse on an external entity subparser, causing a later parse to crash the application. ## Remediation - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/libexpat/libexpat/pull/1444 - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: disclosure@vulncheck.com) — https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: disclosure@vulncheck.com) — https://github.com/libexpat/libexpat/pull/1444 - fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: disclosure@vulncheck.com) — https://www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-via-external-entity-subparser ## Affected products and versions - libexpat / libexpat (libexpat/libexpat): ≥ 0; ≤ 2.9.0 (affected, semver). Source: CNA: VulnCheck ## NVD configuration conditions Affected CPE matches depend on the following AND/OR and negation conditions: ```json [ { "negate": false, "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*", "versionEndIncluding": "2.9.0", "vulnerable": true } ], "negate": false, "operator": "OR" } ], "operator": "OR" } ] ``` ## Severity and prioritization - CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck - CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck - CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: nvd@nist.gov - CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: disclosure@vulncheck.com - CISA KEV: No listing in collected sources - EPSS: 0.43% as of 2026-11-05; percentile 36.99% - SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP - Weaknesses: CWE-476 ## Exploit evidence No exploit evidence in collected sources. This is not proof of no exploitation. ## References - https://github.com/libexpat/libexpat/pull/1444 (CNA: VulnCheck; patch, issue-tracking) - https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d (CNA: VulnCheck; patch) - https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L3468-L3510 (CNA: VulnCheck; technical-description) - https://github.com/libexpat/libexpat (CNA: VulnCheck; product) - https://www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-via-external-entity-subparser (CNA: VulnCheck; third-party-advisory) - https://github.com/libexpat/libexpat (disclosure@vulncheck.com; Product) - https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L3468-L3510 (disclosure@vulncheck.com; Product) - https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d (disclosure@vulncheck.com; Patch) - https://github.com/libexpat/libexpat/pull/1444 (disclosure@vulncheck.com; Patch) - https://www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-via-external-entity-subparser (disclosure@vulncheck.com; Patch, Vendor Advisory) ## Provenance - CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-117610; retrieved 2026-11-05; source updated 2026-11-05 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-117610; retrieved 2026-11-05; source updated 2026-11-05 - FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-117610; retrieved 2026-11-05; source updated Not reported Revision: f2529af795b3897dd93744830202fe973772cb8c0bd0abcd60a9bc38e8b55c3c Canonical: https://y2.dev/cve/CVE-2026-117610 ## Agent and API access Public CVE pages, Markdown, and JSON are free to read without an account or API key. - Public catalog: https://y2.dev/cve/index.json. 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