7.5

CVE-2025-38523: cifs: Fix the smbd_response slab to allow usercopy

Modified
AliasesUBUNTU-CVE-2025-38523DEBIAN-CVE-2025-38523
Published 16-08-2025Last modified 05-08-2026

Vulnerability summary

CVE-2025-38523 is a high (CVSS 7.5) vulnerability in linux. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 30.6% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 7.5 (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
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.01 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 7 · Related 6
RHSA-2025:16904USN-7833-1USN-7833-2USN-7833-3USN-7833-4USN-7834-1

Timeline

  1. 16-08-2025
    PublishedVulnerability first disclosed.
  2. 05-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

31%

Versus all other CVEs

30-day change

Increase +0.01 pp

From 0.35% 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.

Ubuntu91 products
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
  • linux-aws-5.13All versions (No fix recorded)
  • linux-aws-5.19All versions (No fix recorded)
Linux2 products
  • linux≥ ee4cdf7ba857a894ad1650d6ab77669cbbfa329e, < 87dcc7e33fc3dcb8ed32333cec016528b5bb6ce4 | ≥ ee4cdf7ba857a894ad1650d6ab77669cbbfa329e, < f0dd353d47f7051afa98c6c60c7486831eb1a410 | ≥ ee4cdf7ba857a894ad1650d6ab77669cbbfa329e, < 43e7e284fc77b710d899569360ea46fa3374ae22 | 6.12
  • linux_kernel≥ 6.12, < 6.12.36 | ≥ 6.13, < 6.15.8 | 6.16:rc1 | 6.16:rc2 | 6.16:rc3
Debian1 product
  • linux< 6.12.37-1

3 vendors · 94 products

References

13 links
Show all 13 references