CVE-2026-52996

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix durable fd leak on ClientGUID mismatch in durable v2 open

ksmbd_lookup_fd_cguid() returns a ksmbd_file with its refcount incremented via ksmbd_fp_get(). parse_durable_handle_context() in the DURABLE_REQ_V2 case properly releases this reference on every path inside the ClientGUID-match branch, either by calling ksmbd_put_durable_fd() or by transferring ownership to dh_info->fp for a successful reconnect. However, when an entry exists in the global file table with the same CreateGuid but a different ClientGUID, the code simply falls through to the new-open path without dropping the reference obtained from ksmbd_lookup_fd_cguid().

Per MS-SMB2 section 3.3.5.9.10 (Handling the SMB2_CREATE_DURABLE_HANDLE_REQUEST_V2 Create Context), the server MUST locate an Open whose Open.CreateGuid matches the requests CreateGuid AND whose Open.ClientGuid matches the ClientGuid of the connection that received the request. If no such Open is found, the server MUST continue with the normal open execution phase. A CreateGuid hit with a ClientGUID mismatch is therefore the Open not found case: proceeding with a new open is correct, but the reference obtained purely as a side effect of the lookup must not be leaked.

Repeated requests that hit this mismatch pin global_ft entries, prevent __ksmbd_close_fd() from ever running for the corresponding files, and defeat the durable scavenger, leading to long-lived resource leaks.

Release the reference in the mismatch path and clear dh_info->fp so subsequent logic does not mistake a non-matching lookup result for a reconnect target.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/06f709d0e531f3e54d88665dd426be3998a774e6
• https://git.kernel.org/stable/c/407b6e699ba8b45b72cc265eed8a1bc8a7191609
• https://git.kernel.org/stable/c/804054d19886ac6628883d82410f6ee42a818664
• https://git.kernel.org/stable/c/8c4a0ef19c8264c150833131af34541495832cd0
• https://git.kernel.org/stable/c/f31beef633fbf2b5af7805fa187a10bcff1d4b49