CVE-2026-64397Use-After-Free RCE in Linux Kernel ksmbd
In the Linux kernel, the following vulnerability has been resolved: ksmbd: serialize QUERY_DIRECTORY requests per file smb2_query_dir() stores a pointer to its stack-allocated private data in the ksmbd_file readdir_data. Concurrent QUERY_DIRECTORY requests using the same file handle can overwrite this pointer while an iterate_dir() callback is still using it, resulting in a stack use-after-free. Add a per-file mutex and hold it while accessing the shared directory enumeration state. The lock covers scan restart, dot entry state, readdir_data setup and iteration, and response construction. This prevents another request from replacing readdir_data.private before the current request has finished using it and also serializes the shared file position.
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A critical use-after-free vulnerability was identified in the Linux kernel's ksmbd (SMB) module. Attackers can trigger this via concurrent directory queries, potentially leading to remote code execution (RCE) at the kernel level.
Relevant roles
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HEPSS
Technical description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: serialize QUERY_DIRECTORY requests per file smb2_query_dir() stores a pointer to its stack-allocated private data in the ksmbd_file readdir_data. Concurrent QUERY_DIRECTORY requests using the same file handle can overwrite this pointer while an iterate_dir() callback is still using it, resulting in a stack use-after-free. Add a per-file mutex and hold it while accessing the shared directory enumeration state. The lock covers scan restart, dot entry state, readdir_data setup and iteration, and response construction. This prevents another request from replacing readdir_data.private before the current request has finished using it and also serializes the shared file position.
References
- https://git.kernel.org/stable/c/1426fd79102539bc0ab5c8fced047ad4313b9908
- https://git.kernel.org/stable/c/2a64dbf9c739ddf7a25a066507597bf89f8f73d2
- https://git.kernel.org/stable/c/64dac2d486ec1eb18dc00968b16a230b6b75ec24
- https://git.kernel.org/stable/c/a1d5d31cad593ea5e1b637f2f39c9ef6d09d1199
- https://git.kernel.org/stable/c/be6d26bf27499977c746abc163659915082348d8
- https://git.kernel.org/stable/c/fd22b039a5a05bc1d6818e9dcd1001fb432a829d