{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40320","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.186Z","datePublished":"2025-12-08T00:46:47.670Z","dateUpdated":"2026-08-05T12:09:34.045Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:09:34.045Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix potential cfid UAF in smb2_query_info_compound\n\nWhen smb2_query_info_compound() retries, a previously allocated cfid may\nhave been freed in the first attempt.\nBecause cfid wasn't reset on replay, later cleanup could act on a stale\npointer, leading to a potential use-after-free.\n\nReinitialize cfid to NULL under the replay label.\n\nExample trace (trimmed):\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110\n[...]\nRIP: 0010:refcount_warn_saturate+0x9c/0x110\n[...]\nCall Trace:\n <TASK>\n smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n ? step_into+0x10d/0x690\n ? __legitimize_path+0x28/0x60\n smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n ? kmem_cache_alloc+0x18a/0x340\n ? getname_flags+0x46/0x1e0\n cifs_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n statfs_by_dentry+0x67/0x90\n vfs_statfs+0x16/0xd0\n user_statfs+0x54/0xa0\n __do_sys_statfs+0x20/0x50\n do_syscall_64+0x58/0x80"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - Both halves of the bug are driven entirely by a remote SMB peer — the server decides when `compound_send_recv()` returns the replayable error (`-EAGAIN`/`-ECONNABORTED`) that reaches `replay_again:`, and it sends the SMB2 lease-break that makes `cached_dir_lease_break()` drop the cfid's last reference and free it. A malicious/compromised file server or an on-path attacker against an SMB session without signing can reach this over the network or WAN.\nAC:L - The server has deterministic control of every precondition: it triggers the replayable error, times the lease break that frees the cfid, and fails its second CREATE so `open_cached_dir()` returns without resetting `*ret_cfid`, leaving the dangling pointer guaranteed. No memory layout or timing condition outside the attacker's control is required, and the replay backoff plus a full round trip give a generous heap-grooming window.\nPR:N - The attacker is the remote SMB server or an on-path attacker and holds no privileges or credentials on the victim system. The client-side entry points (`statfs`, `getxattr`, `listxattr`) need only an unprivileged user and in practice fire unprompted from `df`, monitoring agents and container runtimes.\nUI:N - The CIFS mount is a standing deployment condition (fstab/autofs/automount in enterprise and NAS setups), not a per-attempt victim action; once it exists the server drives the entire sequence itself. It only needs to wait for a routine `statfs()`/xattr operation, which recurs continuously without any user acting.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority as the vulnerable cifs client code. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - On replay the stale `cfid->fid.persistent_fid` and `volatile_fid` are read from freed slab memory and transmitted verbatim to the attacker's server in the SMB2 QUERY_INFO request, a repeatable kernel-heap infoleak usable to defeat KASLR. Controlling the reallocated object escalates this to arbitrary kernel memory disclosure.\nI:H - Reaching `close_cached_dir()` on the dangling pointer runs `list_del(&cfid->entry)` with attacker-supplied `next`/`prev` (classic unlink arbitrary write), `cfid->cfids->num_entries--`, `dput()` on a forged dentry, and `kfree(cfid->path)` plus an arbitrary-free loop over the dirents list. Together these yield arbitrary write and arbitrary free, sufficient for control-flow hijack and privilege escalation.\nA:H - The reported trace shows `refcount_t: underflow; use-after-free` with a WARNING in `refcount_warn_saturate()` reached from `smb2_query_info_compound()` via `statfs`. Operating on the freed object readily oopses or panics the kernel, and the server can retrigger it at will."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2ops.c"],"versions":[{"version":"433042a91f9373241307725b52de573933ffedbf","lessThan":"939c4e33005e2a56ea8fcedddf0da92df864bd3b","status":"affected","versionType":"git"},{"version":"4f1fffa2376922f3d1d506e49c0fd445b023a28e","lessThan":"327f89c21601ebb7889f8c97754b76f08ce95a0c","status":"affected","versionType":"git"},{"version":"4f1fffa2376922f3d1d506e49c0fd445b023a28e","lessThan":"b556c278d43f4707a9073ca74d55581b4f279806","status":"affected","versionType":"git"},{"version":"4f1fffa2376922f3d1d506e49c0fd445b023a28e","lessThan":"5c76f9961c170552c1d07c830b5e145475151600","status":"affected","versionType":"git"},{"version":"6.6.32","lessThan":"6.6.117","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2ops.c"],"versions":[{"version":"6.8","status":"affected"},{"version":"0","lessThan":"6.8","status":"unaffected","versionType":"semver"},{"version":"6.6.117","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.58","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.17.8","lessThanOrEqual":"6.17.*","status":"unaffected","versionType":"semver"},{"version":"6.18","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.32","versionEndExcluding":"6.6.117"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.12.58"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.17.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.18"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/939c4e33005e2a56ea8fcedddf0da92df864bd3b"},{"url":"https://git.kernel.org/stable/c/327f89c21601ebb7889f8c97754b76f08ce95a0c"},{"url":"https://git.kernel.org/stable/c/b556c278d43f4707a9073ca74d55581b4f279806"},{"url":"https://git.kernel.org/stable/c/5c76f9961c170552c1d07c830b5e145475151600"}],"title":"smb: client: fix potential cfid UAF in smb2_query_info_compound","x_generator":{"engine":"bippy-1.2.0"}}}}