Executive brief
A vulnerability exists in the Linux kernel's SMB client that could cause a system crash. When the system attempts to retry a failed file synchronization command, it may incorrectly try to release the same memory twice. This issue can lead to system instability or a complete denial of service for affected Linux machines.
Technical details
A double-free vulnerability exists in fs/smb/client/smb2pdu.c within the SMB2_flush() function. The issue occurs because response buffer bookkeeping is maintained across replay attempts; if a replayable flush response is received but a subsequent retry fails before a replacement response is stored, the cleanup routine frees the stale response pointer a second time. Attackers could potentially trigger this via specific network conditions or malformed SMB responses that force replay loops. The fix involves reinitializing the response buffer type and I/O vector at the start of the replay loop to ensure cleanup only processes state from the current attempt.
Affected products
- Linux Linux 6.6.32 to 6.6.145, 6.8 to 7.2-rc1
Timeline
- 2026-07-25: advisory: NVD publication date
- 2026-07-25: patched: Fixes merged into multiple stable branches
References
- https://git.kernel.org/stable/c/013a9a3da46c5dabcf18f65ea6a47874ba12a15d
- https://git.kernel.org/stable/c/3407240cde132a4b72d6429a2625a09a2f78adaf
- https://git.kernel.org/stable/c/4be31c943a3a27a5a0251dbb8f5cb89059ec3d5a
- https://git.kernel.org/stable/c/6e27f40b682a5e42a2daae3ce6d96f0e0e16dedb
- https://git.kernel.org/stable/c/878757163eea684750107a31ea134c103863515d