7.7

CVE-2026-52906: 9p: fix access mode flags being ORed instead of replaced

Analyzed
AliasesUBUNTU-CVE-2026-52906DEBIAN-CVE-2026-52906
Published 09-06-2026Last modified 05-08-2026

Vulnerability summary

CVE-2026-52906 is a high (CVSS 7.7) vulnerability in linux. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 1.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.7, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.7/10
010
High · v3.1 (CVE.org)
EPSS score
0.12%
0%100%
Low · -0.06 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 7
OPENSUSE-SU-2026:11014-1USN-8488-1USN-8488-2USN-8489-1USN-8507-1USN-8569-1

Timeline

  1. 09-06-2026
    PublishedVulnerability first disclosed.
  2. 05-08-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: 9p: fix access mode flags being ORed instead of replaced Since commit 1f3e4142c0eb ("9p: convert to the new mount API"), v9fs_apply_options() applies parsed mount flags with |= onto flags already set by v9fs_session_init(). For 9P2000.L, session_init sets V9FS_ACCESS_CLIENT as the default, so when the user mounts with "access=user", both bits end up set. Access mode checks compare against exact values, so having both bits set matches neither mode. This causes v9fs_fid_lookup() to fall through to the default switch case, using INVALID_UID (nobody/65534) instead of current_fsuid() for all fid lookups. Root is then unable to chown or perform other privileged operations. Fix by clearing the access mask before applying the user's choice.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.12%

Chance of exploitation in the next 30 days

Percentile

2%

Versus all other CVEs

30-day change

Decrease -0.06 pp

From 0.18% 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, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu99 products
  • linux< 7.0.0-27.27
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 7.0.0-1008.8
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 1f3e4142c0eb178089ea0cbc97506a061470ad27, < b8f037e87a083291190204b959cda417aaf01058 | ≥ 1f3e4142c0eb178089ea0cbc97506a061470ad27, < da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9 | 6.19
  • linux_kernel≥ 6.19, < 7.0.4
Debian1 product
  • linux< 7.0.4-1

3 vendors · 102 products

References

12 links
Show all 12 references