Linux kernel CIFS truncation sets wrong file size on failed open
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 4 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
The Linux kernel from 6.18 CIFS client updates the inode size in cifs_do_truncate before the server confirms the truncation. If the following open fails, the local inode keeps size 0 while the server file is unchanged.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
In the Linux kernel, the following vulnerability has been resolved: cifs: don't update i_size in cifs_do_truncate without a cached handle If find_writable_file() returns null, cifs_file_flush will return 0 without issuing set_file_size, and the outer 'if (!rc)' block will set i_size to 0 before telling the server to truncate. If the cifs_open() then fails, the inode will have size 0, while the server file is unchanged. Move the netfs_resize_file() and cifs_setsize() into the 'if (cfile)', so they only run after a successful set_file_size. In the no-handle else branch, evict stale pages with truncate_inode_pages before the O_TRUNC open to dispose of old cache pages, and let the open response set the i_size.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
The Linux kernel is fixed in 6.18.59, 7.2.13 and 7.3. Red Hat lists no fix available for Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 and Red Hat OpenShift Container Platform 5.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Linux (Linux) Fixed in 6.18.59, 7.2.13, 7.3
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Not affected: 5 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4
Timeline
- 2026-10-28 Threatist record created from CVE-2026-99137
- 2026-10-28 Alias added: GHSA-4m2c-p8vw-33gr
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-30 CVSS score added · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
- 2026-11-01 Affected versions changed · Red Hat
References
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Sources
- CVE-2026-99137 · CVE Program
- CVE-2026-99137 · NVD
- FIRST EPSS
- GHSA-4m2c-p8vw-33gr · GitHub Advisory Database · CC BY 4.0
- CVE-2026-99137 · Red Hat security data · CC BY 4.0
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