CVE-2026-118370
libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes
- State
- Published
- Severity
- 8.2 High
- Published
- Oct 28, 2026
- Updated
- Oct 28, 2026
- Reserved
- Oct 28, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 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 | 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 | VulnCheck |
Weaknesses
- CWE-190 Integer Overflow or Wraparound
Affected Products
| Product | Versions |
|---|---|
libexpatlibexpat |
|
References
- https://github.com/libexpat/libexpat/pull/1450patchissue-tracking
- https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750aepatch
- https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04cpatch
- https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140technical-description
- https://github.com/libexpat/libexpatproduct
- VulnCheck Advisory: libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixesthird-party-advisory
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