9.8

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

Modified
AliasesUBUNTU-CVE-2025-38527DEBIAN-CVE-2025-38527
Published 16-08-2025Last modified 15-10-2026

Vulnerability summary

CVE-2025-38527 is a critical (CVSS 9.8) Use After Free vulnerability in debian debian_linux. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 37.4% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.8 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.43%
0%100%
Low · +0.02 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 63 · Related 48
DLA-4328-1OPENSUSE-SU-2025:20081-1RHSA-2025:16880RHSA-2025:16904RHSA-2025:17122RHSA-2025:17123

Timeline

  1. 16-08-2025
    PublishedVulnerability first disclosed.
  2. 15-10-2026
    Last modifiedVulnerability information updated.

Description

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 metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.43%

Chance of exploitation in the next 30 days

Percentile

37%

Versus all other CVEs

30-day change

Increase +0.02 pp

From 0.41% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu146 products
  • linuxAll versions (No fix recorded) | < 5.15.0-163.173 | < 6.8.0-100.100
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 5.15.0-1097.104 | < 6.8.0-1046.49
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian2 products
  • linux< 6.1.147-1 | < 6.12.41-1 | < 6.16.3-1
  • debian_linuxEOL11.0
Linux2 products
  • linux≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < 4256a483fe58af66a46cbf3dc48ff26e580d3308 | ≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < 0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b | ≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < 2baaf5bbab2ac474c4f92c10fcb3310f824db995 | ≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < 09bce2138a30ef10d8821c8c3f73a4ab7a5726bc | ≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < da11bd4b697b393a207f19a2ed7d382a811a3ddc | ≥ b98749cac4a695f084a5ff076f4510b23e353ecd, < 705c79101ccf9edea5a00d761491a03ced314210 | 2429fcf06d3cb962693868ab0a927c9038f12a2d | 1ee4f2d7cdcd4508cc3cbe3b2622d7177b89da12 | 53fc31a4853e30d6e8f142b824f724da27ff3e40 | 8092ecc306d81186a64cda42411121f4d35aaff4 | ebac4d0adf68f8962bd82fcf483936edd6ec095b | ≥ 3.16.72, < 3.17 | ≥ 4.9.171, < 4.10 | ≥ 4.14.114, < 4.15 | ≥ 4.19.37, < 4.20 | ≥ 5.0.10, < 5.1 | 5.1
  • linux_kernel≥ 3.16.72, < 3.17 | ≥ 4.9.171, < 4.10 | ≥ 4.14.114, < 4.15 | ≥ 4.19.37, < 4.20 | ≥ 5.0.10, < 5.1 | ≥ 5.1.1, < 5.15.190 | ≥ 5.16, < 6.1.147 | ≥ 6.2, < 6.6.100 | ≥ 6.7, < 6.12.40 | ≥ 6.13, < 6.15.8 | 5.1 | 5.1:rc6 | 5.1:rc7 | 6.16:rc1 | 6.16:rc2 | 6.16:rc3 | 6.16:rc4 | 6.16:rc5 | 6.16:rc6

3 vendors · 150 products

References

43 links
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