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CVE-2026-76641— Expat Out-of-Bounds Read via dtdCopy

Quick assessment

Affected
libexpat libexpat
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libexpat是libexpat团队开源的一款轻量级的XML解析库。 libexpat 2.8.3及之前版本存在缓冲区错误漏洞，该漏洞源于处理通过XML_ExternalEntityParserCreate创建的外部实体解析器时，ELEMENT_TYPE成员结构大小不匹配导致storeAtts越界读取attIndex成员，可能导致非CDATA属性空白规范化失败或野指针解引用导致段错误。

CVSS 7.5 · High EPSS 0.35% · P27

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
libexpat libexpat ≤ 2.8.3 affected
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I. Basic Information for CVE-2026-76641

Vulnerability Information
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Vulnerability Title
Expat Out-of-Bounds Read via dtdCopy
Source: CVE Program / CVE List V5
Vulnerability Description
Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
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
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
libexpat 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libexpat是libexpat团队开源的一款轻量级的XML解析库。 libexpat 2.8.3及之前版本存在缓冲区错误漏洞，该漏洞源于处理通过XML_ExternalEntityParserCreate创建的外部实体解析器时，ELEMENT_TYPE成员结构大小不匹配导致storeAtts越界读取attIndex成员，可能导致非CDATA属性空白规范化失败或野指针解引用导致段错误。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
libexpat libexpat 0 ~ 2.8.3 -

II. Public POCs for CVE-2026-76641

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 8775 chars
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III. Intelligence Information for CVE-2026-76641

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Patches & Fixes for CVE-2026-76641 (2)

Vendor Advisories for CVE-2026-76641 (1)

IV. Related Vulnerabilities

Same product: libexpat
Same vendor: libexpat
Same weakness: CWE-125

V. Comments for CVE-2026-76641

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