CVE-2026-115506ImportantNetworkRevised 26 Oct

libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

MSRC advisory NVD CVE.org

Assessment

Severity: Important
CVSS base score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Impact: Not stated
EPSS, next 30 days: Not scored yet
Public exploit code: No Nuclei template lists it
Exploitability: Not assessed
Publicly disclosed: No
Customer action: Required: apply the update
Component: Mariner
Weakness: CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Issued by: VulnCheck
Published: 24 Oct 2026 · October 2026
Last revised: 26 Oct 2026Information published.

CVSS 3.1 base metricsRed raises the risk · green lowers it

Attack vector: NetworkAV:N
Attack complexity: LowAC:L
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

MSRC lists no downloadable update, which usually means a service-side fix or a release-notes update. Check the MSRC advisory.

Affected products

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

First observed 24 Oct 2026

26 Oct 2026 · 07:26:10 UTC Last revised25 Oct 2026 01:01 UTC → 26 Oct 2026 01:48 UTC
26 Oct 2026 · 07:26:10 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
25 Oct 2026 · 07:41:18 UTC Last revised24 Oct 2026 01:01 UTC → 25 Oct 2026 01:01 UTC

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Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-115506

Published

libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

libexpat through 2.9.0 contains a denial of service vulnerability because billion laughs protection in accountingDiffTolerated() in xmlparse.c detects entity amplification too late. Attackers can supply a moderately sized XML document with a large DTD and nested entity expansions to consume tens of seconds of CPU per parse.

Source published: 22 Oct 2026 19:14:06 UTC
Source modified: 23 Oct 2026 21:06:43 UTC
Observed here: 23 Oct 2026 22:48:20 UTC
Source terms: CVE Program Terms of Use

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

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CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H