CVE-2025-38523: Linux kernel · cifs: Fix the smbd_response slab to allow usercopy
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.5 High · fixed in 6.14.0-1015.15~24.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.14.0-1015.15~24.04.1, 6.14.0-1014.14~24.04.1, 6.14.0-1007.7 +3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7833-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7834-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7856-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-azure-6.14pkg:deb/ubuntu/linux-azure-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-nvidia-6.14pkg:deb/ubuntu/linux-azure-nvidia-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcp-6.11pkg:deb/ubuntu/linux-gcp-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: cifs: Fix the smbd_response slab to allow usercopy The handling of received data in the smbdirect client code involves using copy_to_iter() to copy data from the smbd_reponse struct's packet trailer to a folioq buffer provided by netfslib that encapsulates a chunk of pagecache. If, however, CONFIG_HARDENED_USERCOPY=y, this will result in the checks then performed in copy_to_iter() oopsing with something like the following: CIFS: Attempting to mount //172.31.9.1/test CIFS: VFS: RDMA transport established usercopy: Kernel memory exposure attempt detected from SLUB object 'smbd_response_0000000091e24ea1' (offset 81, size 63)! ------------[ cut here ]------------ kernel BUG at mm/usercopy.c:102! ... RIP: 0010:usercopy_abort+0x6c/0x80 ... Call Trace: <TASK> __check_heap_object+0xe3/0x120 __check_object_size+0x4dc/0x6d0 smbd_recv+0x77f/0xfe0 [cifs] cifs_readv_from_socket+0x276/0x8f0 [cifs] cifs_read_from_socket+0xcd/0x120 [cifs] cifs_demultiplex_thread+0x7e9/0x2d50 [cifs] kthread+0x396/0x830 ret_from_fork+0x2b8/0x3b0 ret_from_fork_asm+0x1a/0x30 The problem is that the smbd_response slab's packet field isn't marked as being permitted for usercopy. Fix this by passing parameters to kmem_slab_create() to indicate that copy_to_iter() is permitted from the packet region of the smbd_response slab objects, less the header space.
References
- ubuntu.com/security/CVE-2025-38523 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-38523 (opens in a new tab)
- git.kernel.org/linus/43e7e284fc77b710d899569360ea46fa3374ae22 (opens in a new tab)
- git.kernel.org/stable/c/43e7e284fc77b710d899569360ea46fa3374ae22 (opens in a new tab)
- git.kernel.org/stable/c/87dcc7e33fc3dcb8ed32333cec016528b5bb6ce4 (opens in a new tab)
- git.kernel.org/stable/c/f0dd353d47f7051afa98c6c60c7486831eb1a410 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7834-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7856-1 (opens in a new tab)