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CVE-2026-124317— libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16

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 2.10.0 及更早版本在 xmltok.c 文件的 unknown_toUtf8() 和 unknown_toUtf16() 函数中存在越界读取漏洞。该漏洞发生在处理应用程序注册的未知编码时。攻击者可构造一个以截断的多字节序列结尾的文档，导致转换回调函数读取解析缓冲区之后的内存，从而泄露相邻内存内容或引发应用程序崩溃。

CVSS 4.8 · Medium
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I. Basic Information for CVE-2026-124317

Vulnerability Information
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Vulnerability Title
libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16
Source: CVE Program / CVE List V5
Vulnerability Description
libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
缓冲区上溢读取
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libexpat libexpat 0 ~ 2.10.0 -

II. Public POCs for CVE-2026-124317

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-124317

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Vendor Pages for CVE-2026-124317 (1)

Other References for CVE-2026-124317 (3)

IV. Related Vulnerabilities

Same product: libexpat
Same vendor: libexpat
Same weakness: CWE-126