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CVE-2026-118370

libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes

publishedCWE-190

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.

Technical severity8.2 highCVSS 4.0 · CNA: VulnCheck
Published2026-10-28Source updated 2026-11-02
Collected2026-11-023 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

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: [email protected]

Fix

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

Source: [email protected]

Fix

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

Source: [email protected]

Fix

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

Source: [email protected]

Affected products and versions

ProductVersionsAuthority
libexpat
libexpat
libexpat/libexpat
github 		≥ 0; ≤ 2.9.0 (affected, semver)
Other versions: unaffected 		CNA: VulnCheck

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

NVD applicability configurations (1)

These expressions retain AND/OR operators, negation, and required environmental products. A listed product is not sufficient to establish exposure when additional conditions apply.

[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*",
            "versionEndIncluding": "2.9.0",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]

CVSS assessments

Version / scoreVectorAuthority
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:NCNA: VulnCheck
3.1 / 5.9
medium		 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HCNA: VulnCheck
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/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:XNVD: [email protected]
3.1 / 8.2
high		 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:HNVD: [email protected]
3.1 / 5.9
medium		 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HNVD: [email protected]

Exploit evidence

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

References

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