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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-72422

ksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE conn->preauth_info is shared connection state (struct preauth_integrity_info, kmalloc-96) that is allocated and freed by the SMB2 NEGOTIATE handler and read by the response send path. smb2_handle_negotiate() allocates conn->preauth_info, and on a deassemble_neg_contexts() failure kfrees it and sets it to NULL. Both the allocation and the free/NULL happen under ksmbd_conn_lock(conn) (the connection srv_mutex), which is held across the whole handler body. The response send path smb3_preauth_hash_rsp(), called from the send: block of __handle_ksmbd_work(), reads conn->preauth_info and dereferences conn->preauth_info->Preauth_HashValue (via ksmbd_gen_preauth_integrity_hash()) without taking conn_lock. When a client drives two SMB2 NEGOTIATE requests on the same connection, one worker can free conn->preauth_info on the failing-negotiate path while a concurrent send-path worker is reading it, producing a slab use-after-free read (KASAN-confirmed). The send-path read tested conn->preauth_info for NULL but raced with the free that occurs between the NULL check and the dereference, so the NULL guard alone does not close the window. Serialize the NEGOTIATE-branch read in smb3_preauth_hash_rsp() under ksmbd_conn_lock(conn) and re-check conn->preauth_info inside the lock. Because the negotiate handler holds conn_lock across its kfree + NULL assignment, a reader that also takes conn_lock either runs fully before the allocation or fully after the NULL store, and can never observe the freed-but-not-yet-NULLed pointer. ksmbd_gen_preauth_integrity_hash() takes no locks itself (it only computes a SHA-512 over the buffer), so no lock-ordering inversion is introduced, and conn_lock is a sleepable mutex which is safe on this send path (it already performs network I/O).

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • dd4e4c811898410e6a3ae3b63207b7c542860907 to < c7bef84740d1d57848c74f6f5b996606e43ea4feaffected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < d0a469122e7bf8338fec1949fb1e8e1290ed8caaaffected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < 7470511d085af1c7a043a60e53d52b512d5a10b1affected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < 16a1ecf39c217e3d164bd32ef2a4f650abc067faaffected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < 77bb0bbfcc4e777ca653174689e5e363f8ee63d1affected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < 1c89da3baa2b1f269178afa87dc30479b8535776affected
  • aa7253c2393f6dcd6a1468b0792f6da76edad917 to < 0c054227479ed7e36ebccb3a558bc0ef698264f6affected
  • 8a8315a5960bd2b5ffc75f44fc089e57c3b17c44affected
  • ff20f1875889dbe4a67c9298e609d7c88cf6456daffected
  • 5.15.61 to < 5.15.212affected
  • 5.18.18 to < 5.19affected
  • 5.19.2 to < 5.20affected

Linux Linux

Default version status: affected

  • 6.0affected
  • 0 to < 6.0unaffected
  • 5.15.212 to ≤ 5.15.*unaffected
  • 6.1.178 to ≤ 6.1.*unaffected
  • 6.6.145 to ≤ 6.6.*unaffected
  • 6.12.97 to ≤ 6.12.*unaffected
  • 6.18.40 to ≤ 6.18.*unaffected
  • 7.1.5 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References