CVE-2025-30156

Ceph's CephX authentication protocol, in versions prior to 20.2.4 and 19.2.6, encrypts authentication tickets with AES-128-CBC in an unauthenticated mode that uses a hard-coded initialization vector and provides no message authentication. An attacker holding one low-privilege CephX key and able to observe CephX traffic can abuse the monitor as an encryption oracle, splicing ciphertext blocks to forge valid tickets for privileged entities such as Manager, MDS, and OSD, or can flip a single bit in a service ticket to set its allow_all field to true. Successful exploitation grants cluster-wide access with high impact on confidentiality and integrity. All Ceph clusters running affected versions are exposed, though the adjacent-network attack vector means an attacker needs access to the network carrying CephX traffic plus a valid low-privilege key. No public proof-of-concept or in-the-wild exploitation is known, and EPSS estimates only a 0.1% probability of exploitation in the next 30 days.

What to do: Upgrade all monitors and clients to Ceph 20.2.4 or 19.2.6, as applicable to your release line. Until upgraded, restrict which hosts can reach the Ceph public/cluster network and audit and minimize CephX key distribution, since exploitation requires an adjacent attacker with a valid low-privilege key who can observe CephX traffic.