Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-93990— Expat through 2.8.4 Malformed UTF-16 Acceptance via Unchecked Surrogate

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.

Expatab 2.8.4 及之前版本未能正确验证 UTF-16 输入中位于高位代理项（high surrogates）之后的低位代理项（low surrogates），从而可能导致格式错误的 UTF-16 序列被接受。攻击者可以构造包含孤立高位代理项的 UTF-16 编码 XML，这些代理项会“消耗”后续的码元，从而隐藏标记字符（如 、 等）对解析器可见，进而实现 XML 注入攻击。

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1029 · Scheduled Transfer
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-93990

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Expat through 2.8.4 Malformed UTF-16 Acceptance via Unchecked Surrogate
Source: CVE Program / CVE List V5
Vulnerability Description
Expat through 2.8.4 fails to validate low surrogates following high surrogates in UTF-16 input, allowing malformed UTF-16 sequences to be accepted. Attackers can craft UTF-16 encoded XML with lone high surrogates that consume following code units, hiding markup characters from the parser and enabling XML injection attacks.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
Unicode编码处理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libexpat libexpat 0 ~ 2.8.4 -

II. Public POCs for CVE-2026-93990

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-93990

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-93990 (2)

Vendor Advisories for CVE-2026-93990 (1)

Vendor Pages for CVE-2026-93990 (1)

IV. Related Vulnerabilities

Same product: libexpat
Same vendor: libexpat
Same weakness: CWE-176

V. Comments for CVE-2026-93990

No comments yet

Leave a comment