Recursive rwsem deadlock in the Linux kernel's ksmbd SMB server subsystem causes ksmbd worker threads to hang indefinitely when any SMB client opens a named pipe, resulting in denial of service for all SMB connections. The flaw was introduced by commit 305853cce3794, which fixed a race condition in RPC handle list access but inadvertently created a deadlock: ksmbd_session_rpc_open acquires sess->rpc_lock as a write lock, then calls ksmbd_rpc_open → ksmbd_session_rpc_method, which attempts to re-acquire the same lock as a read lock - blocking the kernel worker thread indefinitely. No public exploit code exists and EPSS is 0.14% (4th percentile), but the trigger is deterministic and reliable against any ksmbd deployment once valid SMB credentials are obtained. This vulnerability is not in CISA KEV.
Information Disclosure
Linux
Red Hat
Suse
NVD
CVSS 3.1
5.5
EPSS
0.1%