Punk::OAuth2::Server up to 0.03 authorize improper authorization

Summaryinfo

A vulnerability categorized as critical has been discovered in Punk::OAuth2::Server up to 0.03. This issue affects the function authorize. The manipulation results in improper authorization. This vulnerability is reported as CVE-2026-75866. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Punk::OAuth2::Server up to 0.03. It has been classified as critical. Affected is the function authorize. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Punk::OAuth2::Server versions through 0.03 for Perl issue access tokens outside a client's registered scopes and grant types because no authorization path reads them. Punk::OAuth2::Server::Store registers scopes and grant_types per client and documents both as client registration. token dispatches on the grant_type in the request body, so a client registered for authorization_code alone can ask for client_credentials, and that arm passes the requested scope straight to the minter, which signs it into the at+jwt access token. authorize copies the query scope into the authorization code record without comparing it against the registration, leaving the optional consent hook as the only check between an arbitrary scope and the issued code. redirect_uris on the same client row is read and enforced. A registered client can obtain a correctly signed token carrying any scope it names, and a resource server running Punk::OAuth2::Checker accepts that token and honours the scope. A client registered without a secret authenticates on its client_id alone, so anyone who knows that identifier can request one.

The advisory is shared for download at metacpan.org. This vulnerability is traded as CVE-2026-75866 since 08/18/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/22/2026). The MITRE ATT&CK project declares the attack technique as T1548.002.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-64293). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• Punk::OAuth2::Server

Version

• 0.03

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• 🔒

CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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