CVE-2026-102633

libexpat 2.7.2 through 2.8.5 Integer Overflow in expat_realloc

publishedCWE-190

libexpat versions 2.7.2 through 2.8.5 contain an integer overflow vulnerability in expat_realloc() function on 32-bit platforms when computing allocation sizes. Attackers supplying malicious XML to applications parsing with vulnerable libexpat can cause heap buffer overflow, memory corruption, or denial of service.

Technical severity8.2 highCVSS 4.0 · CNA: VulnCheck

Published2026-09-29Source updated 2026-11-10

Collected2026-11-102 attributed sources

Fixes and workarounds

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: CNA: VulnCheck

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: CNA: VulnCheck

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
libexpat libexpat	≥ 2.7.2; ≤ 2.8.5 (affected, semver) Other versions: unaffected	CNA: VulnCheck
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
4.0 / 8.2 high	`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`	CNA: VulnCheck
3.1 / 5.9 medium	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`	CNA: VulnCheck

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://github.com/libexpat/libexpat/pull/1392CNA: VulnCheck · issue-tracking, patch
https://github.com/libexpat/libexpat/commit/209801d7fbaf07ab74bae8cb32dd2ab9e5846118CNA: VulnCheck · patch
https://github.com/libexpat/libexpat/blob/R_2_8_5/expat/lib/xmlparse.c#L1003CNA: VulnCheck · technical-description
https://github.com/libexpat/libexpatCNA: VulnCheck · product
https://www.vulncheck.com/advisories/libexpat-2.7.2-through-2.8.5-integer-overflow-in-expat-reallocCNA: VulnCheck · third-party-advisory
https://cert-portal.siemens.com/productcert/html/ssa-457936.htmlADP: siemens-SADP

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