cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · High
- Fix status
- Partial Red Hat: 5 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.273, 5.15.224, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. 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 8 | 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: 2 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-02 Threatist record created from CVE-2026-89640
- 2026-10-03 Alias added: GHSA-hwfc-7pp7-m5j3
- 2026-10-16 Affected versions changed · Red Hat
- 2026-10-16 CVSS score changed · Red Hat
- 2026-10-18 CISA SSVC decision points changed
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-30 Fix available: Linux/Linux@2c6eede83b3de1268db92c7e49741761c954aa26, Linux/[email protected], Linux/[email protected] +1 · CNA
- 2026-10-30 2 new references · CNA
- 2026-10-30 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/2c6eede83b3de1268db92c7e49741761c954aa26
- https://git.kernel.org/stable/c/ce813e5eebf46851e872ce59bdc34dc5dd4e29a4
- https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4
- https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322
- https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6
- https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028
- https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db
- https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68
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Sources
- CVE-2026-89640 · CVE Program
- CVE-2026-89640 · NVD
- FIRST EPSS
- GHSA-hwfc-7pp7-m5j3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-89640 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences