Use of a broken cryptographic algorithm vulnerability in Ceph RGW's STS session token handling. The STS tokens use the same unauthenticated AES-128-CBC handler as CephX (CVE-2025-30156) and share its lack of integrity protection. An attacker holding any valid STS token can use CBC bit-flipping to modify the token contents without detection, obtaining full RGW admin access. Unlike the CephX attack which requires access to the internal cluster network and a Ceph monitor, this attack is a self-contained modification of a token the attacker already holds, requiring only a single valid unprivileged STS token and STS to be enabled.

Improper verification of cryptographic signature vulnerability in Ceph RGW's SigV4 handler. The flaw is caused by RGW only verifying the validity of headers listed in X-Amz-SignedHeaders without checking whether additional unsigned x-amz- headers are present on the request. AWS S3 requires every x-amz- header to be signed and rejects requests carrying unsigned headers, but RGW does not enforce this check. An attacker holding only a presigned PUT URL can attach arbitrary x-amz- headers that RGW applies, granting more capabilities than the original signer intended, resulting in privilege escalation.