CVE-2026-93990
Description
A flaw was found in Expat. This vulnerability allows a remote attacker to send specially crafted UTF-16 encoded XML data. Due to improper validation of surrogate characters, the parser can be tricked into accepting malformed sequences, which can hide legitimate markup characters. This could enable XML injection attacks, potentially leading to information disclosure or other integrity impacts.
Statement
This is an Important flaw in Expat, which can lead to XML injection. The vulnerability arises from improper validation of UTF-16 surrogate pairs, allowing attackers to craft malformed XML that can bypass parser security checks. This could result in data integrity compromise in applications processing untrusted XML input.
Mitigation
To mitigate this restrict which hosts can send XML (including UTF-16) to Expat-based services with a host firewall and network segmentation. Where applications allow, prefer UTF-8-only input and reject unexpected encodings.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Understanding the Weakness (CWE)
Integrity
Technical Impact: Unexpected State
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
