erlef oidcc 3.2.0-beta.1 JARM data authenticity

Summaryinfo

A vulnerability marked as critical has been reported in erlef oidcc 3.2.0-beta.1. Affected by this issue is the function oidcc_jwt_util.verify_decrypted_token/oidcc_token.int_validate_jwt of the component JARM Handler. The manipulation leads to data authenticity. This vulnerability is traded as CVE-2026-75759. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in erlef oidcc 3.2.0-beta.1. It has been rated as critical. This issue affects the function oidcc_jwt_util.verify_decrypted_token/oidcc_token.int_validate_jwt of the component JARM Handler. The manipulation with an unknown input leads to a data authenticity vulnerability. Using CWE to declare the problem leads to CWE-345. The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Improper Verification of Cryptographic Signature vulnerability in erlef oidcc allows an unauthenticated attacker to impersonate an arbitrary user via an encrypted ID token or JARM response carrying no nested signature. OpenID Connect Core 1.0 section 2 requires that an encrypted ID token be signed then encrypted, with the result being a Nested JWT, and JARM processing rule 5 requires the client to check the signature unconditionally. oidcc instead accepted a JWE wrapping unsigned claims as fully validated, so anyone holding the relying party's public encryption key could mint a token with an arbitrary sub, iss, and aud without possessing the provider's signing key. In oidcc_jwt_util:verify_decrypted_token/4, a decrypted payload that is not a signed JWS fell back to parsing the plaintext claims and returning them with no verifying key. oidcc_token:int_validate_jwt/4 then matched on the JOSE structure type rather than on whether a signature had been verified, and returned success. The JARM path in oidcc_token:validate_jarm/3 is reachable through the browser front channel. UserInfo responses are not affected, because OpenID Connect Core 1.0 section 5.3.2 permits them to be encrypted without also being signed. This issue affects oidcc: from 3.2.0-beta.1 before 3.9.0.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-75759 since 08/21/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 3.9.0 eliminates this vulnerability.

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Productinfo

Vendor

• erlef

Name

• oidcc

Version

• 3.2.0-beta.1

Website

• Product: https://github.com/erlef/oidcc/

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