CVE-2026-75866 Punk::OAuth2::Server versions through 0.03 for Perl issue access tokens outside a client's registered scopes and grant types because no auth
Attackers can obtain access tokens with unauthorized scopes or grant types, bypassing OAuth2 authorization checks in Punk::OAuth2::Server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-75866?
CVE-2026-75866 is a critical missing authorization vulnerability, published on 22 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-862
Which versions are affected by CVE-2026-75866?
How do I fix CVE-2026-75866?
No fix has been published for CVE-2026-75866 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-75866 being exploited?
There is no known exploitation of CVE-2026-75866 in the wild and no public exploit code.
Sources
Also known as GHSA-cjjx-w599-qf62.