CVE-2026-24400: Assertj XML external entity (XXE) (CVSS 9.1)

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

Assertj≥ 1.4.0 < 3.27.7

Remediation

Fixed in

Assertj≥ 3.27.7

Patch & vendor advisories

References

https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.htmlTechnical Description
https://github.com/assertj/assertj/commit/85ca7eb6609bb179c043b85ae7d290523b1ba79aPatch
https://github.com/assertj/assertj/releases/tag/assertj-build-3.27.7ProductRelease Notes
https://github.com/assertj/assertj/security/advisories/GHSA-rqfh-9r24-8c9rMitigationVendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-24400 being actively exploited?

CVE-2026-24400 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.58%.

How severe is CVE-2026-24400?

CVE-2026-24400 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.58% probability of exploitation.

Which products are affected by CVE-2026-24400?

Affected products include Assertj.

How do I fix CVE-2026-24400?

Upgrade affected software to a fixed version, for example Assertj 3.27.7 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-24400 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation works Book a demo