EUVD-2026-76551
GHSA-m6p4-6vjr-qq2h
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Local access and low privileges required for CIFS mount access; no scope change; confidentiality and integrity both high due to stale cache data exposure and cache inconsistency.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC
cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it cannot use cifs_resize_file_locked() to perform a proper fscache cookie resize. Instead, add cifs_invalidate_cache() after cifs_setsize().
cifs_invalidate_cache() calls fscache_invalidate(), which works without holding i_rwsem: it unconditionally increments inval_counter and sets FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not served once the cookie is later activated by fscache_use_cookie(). Truncation to zero leaves no valid cached data, making invalidation the correct semantic here.
AnalysisAI
Stale fscache data exposure in the Linux kernel CIFS client allows a local low-privileged user with access to a mounted SMB share to read file data that should have been discarded after an O_TRUNC open. When cifs_do_truncate() is called from cifs_open() without holding i_rwsem, the fscache cookie invalidation step is skipped - meaning previously cached file contents remain readable via fscache_use_cookie() even after the file has been truncated to zero. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires local user access (AV:L) with at least low privileges (PR:L - a regular unprivileged user account). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Real-world risk is moderate. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released patches: upgrade to Linux 6.18.50, 7.2.4, or 7.3-rc1 as appropriate for the deployed branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all systems running Linux with CIFS/SMB mounts and catalog the local user base and data sensitivity on affected shares. …
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External POC / Exploit Code
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