CVE-2026-24400: AssertJ provides Fluent testing assertions for Java and the Java Virtual Machine (JVM)

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CRITICAL 9.1REMOTEUPGRADE

CVE-2026-24400 is a critical-severity flaw (CVSS 9.1) affecting assertj. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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)` a

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-611
Published	2026-01-26
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: assertj

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-01-26 23:16 UTCPublished CVE record published
2026-06-17 10:23 UTCUpdated Record last modified

assertj assertj UPGRADE

Affected: >= 1.4.0 and < 3.27.7

Fixed in: 3.27.7

Safe to downgrade to: a release before 1.4.0

1. Check installed version

apt-cache policy assertj || rpm -q assertj || assertj --version

2. UPGRADE to 3.27.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade assertj

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade assertj

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.4.0 (Debian / Ubuntu)

apt-cache madison assertj sudo apt install assertj=<VERSION_BEFORE_1.4.0> sudo apt-mark hold assertj

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list assertj sudo dnf downgrade assertj-<VERSION_BEFORE_1.4.0> sudo dnf versionlock add assertj

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-24400?

assertj: upgrade to 3.27.7. Exact commands for each OS are on this page.

Is CVE-2026-24400 being exploited?

CVE-2026-24400 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-24400 affect?

CVE-2026-24400 affects assertj. Severity is critical (CVSS 9.1). 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.XmlStringPrettyFo

How urgent is CVE-2026-24400?

Priority 49/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Java vulnerabilities

References

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