CVE-2026-72889

Net::OAuth versions before 0.33 for Perl allow the sender to choose the signature algorithm in verify.

verify resolves the signature method class from the signaturemethod parameter of the incoming message. signaturemethod is required on every request, so the algorithm used to check a signature is chosen by whoever sent it, and nothing lets the verifying party pin the method instead. When a message names HMAC-SHA1 or HMAC-SHA256, the key is derived from consumersecret and tokensecret rather than from the key the provider deployed.

A provider deployed on RSA-SHA1 holds only the consumer public key, and RFC 5849 does not use consumer_secret for that method, so the required parameter is filled with a placeholder. A client that names HMAC-SHA1 instead has its signature checked against that placeholder, so a guessable one is enough to forge requests for any consumer key and token.