How severe is CVE-2026-24400?

No CVSS score has been assigned to CVE-2026-24400 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-24400?

CVE-2026-24400 affects the following packages: org.assertj:assertj-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-24400?

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.

How do I detect CVE-2026-24400 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.assertj:assertj-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-24400 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2026-24400?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-24400 can be triaged on real exposure rather than presence alone.

Is CVE-2026-24400 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-24400 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-24400?

CVE-2026-24400 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 44th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-24400?

CVE-2026-24400 is classified as XML External Entity (XXE) (CWE-611). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-24400 published, and has it been updated?

CVE-2026-24400 was published on January 26, 2026 and was last updated on August 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2026-24400 — assertj-core

Fix: assertj/assertj@85ca7eb

CVE-2026-24400 is a XML External Entity (XXE) vulnerability in org.assertj:assertj-core. A fix is available for org.assertj:assertj-core — see the affected versions and patch details below.

AssertJ has XML External Entity (XXE) vulnerability when parsing untrusted XML via isXmlEqualTo assertion

Also known asGHSA-rqfh-9r24-8c9r

Published

Jan 26, 2026

Updated

Aug 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-24400.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk

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.

Real-World Exposure

1 pkg affected

☕org.assertj:assertj-core

Real-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

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 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, or
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.

References

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.assertj:assertj-core`	≥ 1.4.0&&< 3.27.7	3.27.7`org.assertj:assertj-core:3.27.7`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.assertj:assertj-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-24400 can be triaged on real exposure rather than presence alone.

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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Exploitation of this vulnerability requires that a user processes untrusted content with the affected package.

Product	Fixed in	Advisory
AMQ Clients 2026.Q3	`assertj-core`	RHSA-2026:69459
Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16	`assertj-core`	RHSA-2026:37390
Red Hat Enterprise Linux 10	`assertj-core-0:3.24.2-9.el10_2.1`	RHSA-2026:59372
Red Hat Enterprise Linux 10.0 Extended Update Support	`assertj-core-0:3.24.2-9.el10_0.1`	RHSA-2026:69106
Red Hat Enterprise Linux 9	`assertj-core-0:3.19.0-9.el9_8.1`	RHSA-2026:60215
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions	`assertj-core-0:3.19.0-5.el9_2.2`	RHSA-2026:58956
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions	`assertj-core-0:3.19.0-5.el9_4.2`	RHSA-2026:58957
Red Hat Enterprise Linux 9.6 Extended Update Support	`assertj-core-0:3.19.0-9.el9_6.1`	RHSA-2026:58949

Frequently Asked Questions

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.XmlStri

O3 Security · Impact-Aware SCA

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