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CVE-2026-115506— libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

Quick assessment

Affected
libexpat libexpat
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libexpat 2.9.0 及之前版本存在拒绝服务漏洞。其 文件中的 函数在检测实体膨胀时响应过晚，导致“十亿次笑声”（Billion Laughs）防护机制失效。攻击者可提供一个中等大小的 XML 文档，其中包含大型 DTD 及嵌套实体展开，从而在解析过程中消耗数十秒的 CPU 时间。

CVSS 7.5 · High EPSS 0.35% · P28

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
libexpat libexpat ≤ 2.9.0 affected
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I. Basic Information for CVE-2026-115506

Vulnerability Information
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Vulnerability Title
libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay
Source: CVE Program / CVE List V5
Vulnerability Description
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: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
DTD中递归实体索引的不恰当限制(XML实体扩展)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libexpat libexpat 0 ~ 2.9.0 -

II. Public POCs for CVE-2026-115506

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-115506

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Patches & Fixes for CVE-2026-115506 (1)

Vendor Advisories for CVE-2026-115506 (1)

Proof of Concept for CVE-2026-115506 (1)

Vendor Pages for CVE-2026-115506 (1)

IV. Related Vulnerabilities

Same product: libexpat
Same vendor: libexpat
Same weakness: CWE-776