CVE-2026-40459: PAC4J is vulnerable to LDAP Injection in multiple methods

This month

HIGH 8.8UPGRADE

CVE-2026-40459 is a high-severity flaw (CVSS 8.8) affecting pac4j. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PAC4J is vulnerable to LDAP Injection in multiple methods. A low-privileged remote attacker can inject crafted LDAP syntax into ID-based search parameters, potentially resulting in unauthorized LDAP queries and arbitrary directory operations. This issue was fixed in PAC4J versions 4.5.10, 5.7.10 and 6.4.1

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-90
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: >= 4.0.0 and < 4.5.10 · >= 5.0.0 and < 5.7.10 · >= 6.0.0 and < 6.4.1

Fixed in: 4.5.10, 5.7.10, 6.4.1

Safe to downgrade to: a release before 4.0.0

1. Check installed version

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

2. UPGRADE to 4.5.10 (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 4.0.0 (Debian / Ubuntu)

apt-cache madison pac4j sudo apt install pac4j=<VERSION_BEFORE_4.0.0> 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_4.0.0> 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-2026-40459?

pac4j: upgrade to 4.5.10, 5.7.10, 6.4.1. Exact commands for each OS are on this page.

Is CVE-2026-40459 being exploited?

CVE-2026-40459 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-2026-40459 affect?

CVE-2026-40459 affects pac4j. Severity is high (CVSS 8.8). PAC4J is vulnerable to LDAP Injection in multiple methods. A low-privileged remote attacker can inject crafted LDAP syntax into ID-based search parameters, potentially resulting in unauthorized LDAP queries and arbitrary directory operation

How urgent is CVE-2026-40459?

Priority 43/100. High severity

Related CVEs

CVE-2026-40458 MEDIUM 6.5 UPGRADE PAC4J is vulnerable to Cross-Site Request Forgery (CSRF)

References

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