CVE-2026-40458: PAC4J is vulnerable to Cross-Site Request Forgery (CSRF)

Routine

MEDIUM 6.5UPGRADE

CVE-2026-40458 is a medium-severity flaw (CVSS 6.5) affecting pac4j. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PAC4J is vulnerable to Cross-Site Request Forgery (CSRF). A malicious attacker can craft a specially designed website which, when visited by a user, will automatically submit a forged cross-site request with a token whose hash collides with the victim's legitimate CSRF token. Importantly, the attacker does not need to know the victim’s CSRF token or its hash prior to the attack. Collisions in the deterministic String.hashCode() function can be co

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-352
Published	2026-04-17
Last modified	2026-06-17

Publisher (CNA): CERT.PL · Vendor: pac4j

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

Am I affected?

Timeline

2026-04-17 14:16 UTCPublished CVE record published
2026-06-17 10:45 UTCUpdated Record last modified

pac4j pac4j UPGRADE

Affected: >= 5.0.0 and < 5.7.10 · > 6.0.0 and < 6.4.1

Fixed in: 5.7.10, 6.4.1

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy pac4j || rpm -q pac4j || pac4j --version

2. UPGRADE to 5.7.10 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pac4j

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pac4j

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 5.0.0 (Debian / Ubuntu)

apt-cache madison pac4j sudo apt install pac4j=<VERSION_BEFORE_5.0.0> sudo apt-mark hold pac4j

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

dnf --showduplicates list pac4j sudo dnf downgrade pac4j-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add pac4j

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-2026-40458?

pac4j: upgrade to 5.7.10, 6.4.1. Exact commands for each OS are on this page.

Is CVE-2026-40458 being exploited?

CVE-2026-40458 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-2026-40458 affect?

CVE-2026-40458 affects pac4j. Severity is medium (CVSS 6.5). PAC4J is vulnerable to Cross-Site Request Forgery (CSRF). A malicious attacker can craft a specially designed website which, when visited by a user, will automatically submit a forged cross-site request with a token whose hash collides with

How urgent is CVE-2026-40458?

Priority 24/100. No elevated risk signals yet.

Related CVEs

CVE-2026-40459 HIGH 8.8 UPGRADE PAC4J is vulnerable to LDAP Injection in multiple methods

References

← Back to latest CVEs