assertj: Improper Restriction of XML External Entity Reference
CVE-2026-24400 is a critical-severity improper restriction of XML external entity reference vulnerability in assertj, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected assertj versions: >= 1.4.0, < 3.27.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of assertj you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.2 | High | CNA (github.com) |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official description
AssertJ provides Fluent testing assertions for Java and the Java Virtual Machine (JVM). Starting in version 1.4.0 and prior to version 3.27.7, 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 either `isXmlEqualTo(CharSequence)` from `org.assertj.core.api.AbstractCharSequenceAssert` or `xmlPrettyFormat(String)` from `org.assertj.core.util.xml.XmlStringPrettyFormatter`. If untrusted XML input is processed by tone of these methods, an attacker couldnread arbitrary local files via `file://` URIs (e.g., `/etc/passwd`, application configuration files); perform Server-Side Request Forgery (SSRF) via HTTP/HTTPS URIs, and/or cause Denial of Service via "Billion Laughs" entity expansion attacks. `isXmlEqualTo(CharSequence)` has been deprecated in favor of XMLUnit in version 3.18.0 and will be removed in version 4.0. Users of affected versions should, in order of preference: replace `isXmlEqualTo(CharSequence)` with XMLUnit, upgrade to version 3.27.7, or avoid using `isXmlEqualTo(CharSequence)` or `XmlStringPrettyFormatter` with untrusted input. `XmlStringPrettyFormatter` has historically been considered a utility for `isXmlEqualTo(CharSequence)` rather than a feature for AssertJ users, so it is deprecated in version 3.27.7 and removed in version 4.0, with no replacement.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of XML External Entity Reference
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
How developers prevent this class of flaw
- Many XML parsers and validators can be configured to disable external entity expansion.
More Improper Restriction of XML External Entity Reference vulnerabilities (CWE-611)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other references
Recent Improper Restriction of XML External Entity Reference vulnerabilities
- 9.8 Critical severity
- 7.5 High severity
- 8.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.4 High severity
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