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CVE-2026-40458

Cross-Site Request Forgery in PAC4J

7.0 HighFix available

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Active

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
Low

Exploit likelihood

0.17%Up 0.1 points since Apr 18, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.0

Cross-Site Request Forgery in PAC4J

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

Record
CVE-2026-40458
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-352
Updated
2026-11-02
EUVDEUVD-2026-23421 7.0

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

Record
EUVD-2026-23421
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-xw5c-jc7x-gf75 7.0

PAC4J has a Cross-Site Request Forgery (CSRF) Vulnerability

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1.

Record
GHSA-xw5c-jc7x-gf75
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-352
Updated
2026-11-02
NVD 7.0

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

Record
CVE-2026-40458
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-352
Updated
2026-11-02
OSV 7.0

Cross-Site Request Forgery in PAC4J

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

Record
CVE-2026-40458
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-352
Updated
2026-11-02
OSVGHSA-xw5c-jc7x-gf75 7.0

PAC4J has a Cross-Site Request Forgery (CSRF) Vulnerability

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 computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent.

This issue was fixed in PAC4J versions 5.7.10 and 6.4.1.

Record
GHSA-xw5c-jc7x-gf75
CVSS 4.0
7.0 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-352
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.pac4j:pac4j-core
Maven
before 5.7.10
5.7.10
org.pac4j:pac4j-core
Maven
6.0.0-RC1 up to 6.4.1
6.4.1
org.pac4j:pac4j-core
Maven
before 5.7.10, plus listed versions
1.4.01.4.11.5.01.5.11.6.0
Show 45 moreShow less
1.6.0-RC11.7.01.7.11.7.21.8.01.8.0-RC11.8.11.8.21.8.31.8.41.8.51.8.61.8.71.8.81.8.91.9.01.9.11.9.21.9.31.9.41.9.51.9.61.9.71.9.81.9.92.0.02.0.0-RC12.0.0-RC22.1.02.2.02.2.12.3.02.3.13.0.03.0.0-RC13.0.0-RC23.0.13.0.23.1.03.2.03.3.03.4.03.5.03.6.03.6.1
5.7.10
org.pac4j:pac4j-core
Maven
6.0.0-RC1 up to 6.4.1, plus listed versions
6.0.06.0.0-RC106.0.0-RC26.0.0-RC36.0.0-RC4
Show 25 moreShow less
6.0.0-RC56.0.0-RC66.0.0-RC76.0.0-RC86.0.0-RC96.0.16.0.26.0.36.0.46.0.4.16.0.56.0.66.1.06.1.16.1.26.1.36.2.06.2.16.2.26.3.06.3.16.3.26.3.36.4.06.4.0-RC1
6.4.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-40458 is a high vulnerability (CVSS 7.0) in Pac4j, published April 17, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.17%, the 5th percentile. Fixed in org.pac4j:pac4j-core 5.7.10.

References

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Left out here: 63 versions. The JSON record has them.

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