5.5

CVE-2026-31704: ksmbd: use check_add_overflow() to prevent u16 DACL size overflow

Modified
AliasesUBUNTU-CVE-2026-31704DEBIAN-CVE-2026-31704CGA-2987-c9pw-2fhx
Published 01-05-2026Last modified 15-10-2026

Vulnerability summary

CVE-2026-31704 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 1.6% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.12%
0%100%
Low · -0.04 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 22 · Related 21
MGASA-2026-0108MGASA-2026-0110OPENSUSE-SU-2026:10793-1USN-8488-1USN-8488-2USN-8507-1

Timeline

  1. 01-05-2026
    PublishedVulnerability first disclosed.
  2. 15-10-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use check_add_overflow() to prevent u16 DACL size overflow set_posix_acl_entries_dacl() and set_ntacl_dacl() accumulate ACE sizes in u16 variables. When a file has many POSIX ACL entries, the accumulated size can wrap past 65535, causing the pointer arithmetic (char *)pndace + *size to land within already-written ACEs. Subsequent writes then overwrite earlier entries, and pndacl->size gets a truncated value. Use check_add_overflow() at each accumulation point to detect the wrap before it corrupts the buffer, consistent with existing check_mul_overflow() usage elsewhere in smbacl.c.

CVSS metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

0.12%

Chance of exploitation in the next 30 days

Percentile

2%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 0.16% 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

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu146 products
  • linuxAll versions (No fix recorded) | < 6.8.0-136.136 | < 7.0.0-27.27
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 6.8.0-1061.64 | < 7.0.0-1008.8
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Chainguard6 products
  • linux-aws-6.18< 6.18.31-r0
  • linux-azure-6.18< 6.18.24-r1 | < 6.18.31-r0
  • linux-gcp-6.18< 6.18.31-r0
  • linux-qemu-6.18< 6.18.24-r3
  • linux-qemu-rc< 7.1_rc3-r0
Linux2 products
  • linux≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < 41e53a773db6342ac9a689ee5ba635c31744c9f0 | ≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < 8d5729350b236896f51379588d9a690b7fafb8db | ≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < e1955a94b6f17f4b058afa955a6f187eb3ed7615 | ≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < 5e7b8f3c539d69b2ed5f2408e2f75e68ce7eef43 | ≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < ef7902be3f215b6bf7babe4dc9dd9a7d57dad7a7 | ≥ e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, < 299f962c0b02d048fb45d248b4da493d03f3175d | 5.15
  • linux_kernel≥ 5.15, < 6.6.136 | ≥ 6.7, < 6.12.84 | ≥ 6.13, < 6.18.25 | ≥ 6.19, < 7.0.2
Debian1 product
  • linux< 6.1.176-1 | < 6.12.85-1 | < 7.0.3-1

4 vendors · 155 products

References

30 links
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