CVE-2026-118370ImportantNetworkRevised 31 Oct

libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes

MSRC advisory NVD CVE.org

Assessment

Severity: Important
CVSS base score: 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Impact: Not stated
EPSS · 30-day forecast: No EPSS score collected
Public detection template: No Nuclei template is listed in the current collected catalog
Exploitation detected: Unknown: not stated by MSRC
Exploitability: Not assessed
Publicly disclosed: Unknown: not stated by MSRC
Customer action: Required: follow the MSRC remediation guidance
Component: Mariner
Weakness: CWE-190: Integer Overflow or Wraparound
Issued by: VulnCheck
Published: 29 Oct 2026 · October 2026
Last revised: 31 Oct 2026Information published.

CVSS 3.1 base metricsRed raises the risk · green lowers it

Attack vector: NetworkAV:N
Attack complexity: HighAC:H
Privileges required: NonePR:N
User interaction: NoneUI:N
Scope: UnchangedS:U
Confidentiality: NoneC:N
Integrity: NoneI:N
Availability: HighA:H

Updates that fix it

0 KBs

No KB listed

No KB update is listed in the collected MSRC record. Check the MSRC advisory for product releases and other remedies.

Affected products

Open Source Software

2 affected products

azl3 cmake 3.30.3-15 on Azure Linux 3.0
azl3 expat 2.8.3-2 on Azure Linux 3.0

What changed

Affected products: azl3 expat 2.8.3-2 on Azure Linux 3.0 → azl3 cmake 3.30.3-15 on Azure Linux 3.0, azl3 expat 2.8.3-2 on Azure Linux 3.0 · Severity: Moderate → Important
31 Oct 2026
Detection template: No Nuclei template listed · Customer action: Required: apply the update → Required: follow the MSRC remediation guidance · Public disclosure: No → Unknown: not stated by MSRC · Exploitation detected: Not reported by MSRC → Unknown: not stated by MSRC
29 Oct 2026

Page history

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Cite this version

Field-level log (8)

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31 Oct 2026 · 08:05:42 UTC Last revised29 Oct 2026 01:01 UTC → 31 Oct 2026 01:11 UTC
31 Oct 2026 · 08:05:42 UTC Affected productsazl3 expat 2.8.3-2 on Azure Linux 3.0 → azl3 cmake 3.30.3-15 on Azure Linux 3.0, azl3 expat 2.8.3-2 on Azure Linux 3.0
31 Oct 2026 · 08:05:42 UTC SeverityModerate → Important
29 Oct 2026 · 20:19:26 UTC Public detection templateNo Nuclei template listed
29 Oct 2026 · 20:19:26 UTC EPSSNot scored → No EPSS score collected
29 Oct 2026 · 20:19:26 UTC Customer actionRequired: apply the update → Required: follow the MSRC remediation guidance
29 Oct 2026 · 20:19:26 UTC Publicly disclosedNo → Unknown: not stated by MSRC
29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → Unknown: not stated by MSRC

Explore global source statements, affected packages and advisory history for CVE-2026-118370. The catalog has a separate collection scope from Microsoft release records.

cve-program · CVE-2026-118370

Published

libexpat

Vendor product

Original vendor version evidence · not evaluated as a NuGet range

{
                    "vendor": "libexpat",
                    "product": "libexpat",
                    "repo": "https://github.com/libexpat/libexpat",
                    "packageURL": "pkg:github/libexpat/libexpat",
                    "defaultStatus": "unaffected",
                    "versions": [
                        {
                            "version": "0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThanOrEqual": "2.9.0"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON