AssertJ has XML External Entity (XXE) vulnerability when parsing untrusted XML via isXmlEqualTo assertion
Date: 2026-01
Affected: maven/org.assertj:assertj-core
Attack vector: ssrf
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2024-46984
CVE-2026-24400
CWE: CWE-611
CVSS:  (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N)

An XML External Entity (XXE) vulnerability exists in `org.assertj.core.util.xml.XmlStringPrettyFormatter`: the `toXmlDocument(String)` method initializes `DocumentBuilderFactory` with default settings, without disabling DTDs or external entities. This formatter is used by the `isXmlEqualTo(CharSequence)` assertion for `CharSequence` values. An application is vulnerable only when it uses untrusted XML input with one of the following methods: - `isXmlEqualTo(CharSequence)` from `org.assertj.core.api.AbstractCharSequenceAssert` - `xmlPrettyFormat(String)` from `org.assertj.core.util.xml.XmlStringPrettyFormatter` ### Impact If untrusted XML input is processed by the methods mentioned above (e.g., in test environments handling external fixture files), an attacker could: - **Read arbitrary local files** via `file://` URIs (e.g., `/etc/passwd`, application configuration files) - **Perform Server-Side Request Forgery (SSRF)** via HTTP/HTTPS URIs - **Cause Denial of Service** via "Billion Laughs" entity expansion attacks ### Mitigation `isXmlEqualTo(CharSequence)` has been deprecated in favor of [XMLUnit](https://www.xmlunit.org/) in version 3.18.0 and will be removed in version 4.0. Users of affected versions should, in order of preference: 1. Replace `isXmlEqualTo(CharSequence)` with XMLUnit, or 2. Upgrade to version 3.27.7, or 3. Avoid using `isXmlEqualTo(CharSequence)` or `XmlStringPrettyFormatter` with untrusted input. `XmlStringPrettyFormatter` has historically been con


Mitigations:

Architectural layers (MAESTRO):