Multiple vulnerabilities were discovered in PyJWT affecting key validation and handling, potentially allowing attackers to forge authentication tokens or disclose sensitive information. These issues involve improper validation of JWK keys during HMAC verification, incorrect handling of redirects when fetching key sets, and improper recognition of certain PEM and DER public key formats. The vulnerabilities affect PyJWT versions prior to 2.13.0-1ubuntu1 and specific listed versions. Ubuntu has released a fixed package version 2.13.0-1ubuntu1 to address these issues.