CVE-2026-24400
AssertJ has XML External Entity (XXE) vulnerability when parsing untrusted XML via isXmlEqualTo assertion
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.assertj:assertj-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.assertj:assertj-core | ≥ 1.4.0&&< 3.27.7 | 3.27.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.assertj:assertj-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.assertj:assertj-core to 3.27.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-24400 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-24400 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-24400. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-24400 in your dependencies?
O3 detects CVE-2026-24400 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.