Critical 9.8Published Aug 16, 2025

CVE-2025-38527smb: client: fix use-after-free in cifs_oplock_break

Updated under an hour ago (Oct 27, 2026, 1:40 AM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free in cifs_oplock_break A race condition can occur in cifs_oplock_break() leading to a use-after-free of the cinode structure when unmounting: cifs_oplock_break() _cifsFileInfo_put(cfile) cifsFileInfo_put_final() cifs_sb_deactive() [last ref, start releasing sb] kill_sb() kill_anon_super() generic_shutdown_super() evict_inodes() dispose_list() evict() destroy_inode() call_rcu(&inode->i_rcu, i_callback) spin_lock(&cinode->open_file_lock) <- OK [later] i_callback() cifs_free_inode() kmem_cache_free(cinode) spin_unlock(&cinode->open_file_lock) <- UAF cifs_done_oplock_break(cinode) <- UAF The issue occurs when umount has already released its reference to the superblock. When _cifsFileInfo_put() calls cifs_sb_deactive(), this releases the last reference, triggering the immediate cleanup of all inodes under RCU. However, cifs_oplock_break() continues to access the cinode after this point, resulting in use-after-free. Fix this by holding an extra reference to the superblock during the entire oplock break operation. This ensures that the superblock and its inodes remain valid until the oplock break completes.

CVSS: 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from b98749cac4a695f084a5ff076f4510b23e353ecd before 4256a483fe58af66a46cbf3dc48ff26e580d3308; from b98749cac4a695f084a5ff076f4510b23e353ecd before 0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b; from b98749cac4a695f084a5ff076f4510b23e353ecd before 2baaf5bbab2ac474c4f92c10fcb3310f824db995; from b98749cac4a695f084a5ff076f4510b23e353ecd before 09bce2138a30ef10d8821c8c3f73a4ab7a5726bc; from b98749cac4a695f084a5ff076f4510b23e353ecd before da11bd4b697b393a207f19a2ed7d382a811a3ddc; from b98749cac4a695f084a5ff076f4510b23e353ecd before 705c79101ccf9edea5a00d761491a03ced314210; 2429fcf06d3cb962693868ab0a927c9038f12a2d; 1ee4f2d7cdcd4508cc3cbe3b2622d7177b89da12; and 8 more ranges	CNA record
linux linux_kernel linux:linux_kernel	from 3.16.72 before 3.17; from 4.9.171 before 4.10; from 4.14.114 before 4.15; from 4.19.37 before 4.20; from 5.0.10 before 5.1; from 5.1.1 before 5.15.190; from 5.16 before 6.1.147; from 6.2 before 6.6.100; and 11 more ranges	NVD
debian debian_linux debian:debian_linux	11.0	NVD

References

References

https://git.kernel.org/stable/c/4256a483fe58af66a46cbf3dc48ff26e580d3308	patch
https://git.kernel.org/stable/c/0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b	patch
https://git.kernel.org/stable/c/2baaf5bbab2ac474c4f92c10fcb3310f824db995	patch
https://git.kernel.org/stable/c/09bce2138a30ef10d8821c8c3f73a4ab7a5726bc	patch
https://git.kernel.org/stable/c/da11bd4b697b393a207f19a2ed7d382a811a3ddc	patch
https://git.kernel.org/stable/c/705c79101ccf9edea5a00d761491a03ced314210	patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html	mailing-list, third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.