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CVE-2026-82462

pac4j-oidc before 6.5.6 Authentication Bypass via Access Token Substitution

MEDIUM
6.5
CVSS Score
Published: August 29, 2026 at 04:35 PM UTC
Updated: September 10, 2026 at 08:08 PM UTC
1 product affected across 1 vendorPAC4J

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

pac4j-oidc before 6.5.6 accepts OIDC callbacks carrying only an access token without authorization code or ID token validation. Attackers can substitute access tokens minted for other clients to create authenticated sessions without proper issuer, audience, nonce, or subject verification.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

PAC4J· PAC4Jmaven
95%
v < 6.5.6
Affected range stops below 6.5.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

Patch
Source: cverecord
https://github.com/pac4j/pac4j/commit/2270c3ff70e93cc43831e75702acd5135531237e
Vendor Advisory
Source: cverecord
https://www.pac4j.org/blog/security-advisory-pac4j-core-oidc-saml.html
Technical Description
Source: cverecord
https://github.com/pac4j/pac4j/blob/pac4j-parent-6.5.5/pac4j-oidc/src/main/java/org/pac4j/oidc/credentials/extractor/OidcCredentialsExtractor.java
Product
Source: cverecord
https://github.com/pac4j/pac4j
Third Party Advisory
Source: cverecord
https://www.vulncheck.com/advisories/pac4j-oidc-before-6.5.6-authentication-bypass-via-access-token-substitution

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-345

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