f2fs: validate compress cache inode only when enabled
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: validate compress cache inode only when enabled F2FS_COMPRESS_INO() uses NM_I(sbi)->max_nid as the synthetic inode number for the compressed page cache inode. That inode only exists when the compress_cache mount option is enabled. When compress_cache is disabled, max_nid is outside the valid inode range. A corrupted directory entry that points to ino == max_nid should therefore be rejected by f2fs_check_nid_range(). However, is_meta_ino() currently treats F2FS_COMPRESS_INO() as a meta inode unconditionally, so f2fs_iget() bypasses do_read_inode() and its nid range check, and instantiates a fake internal inode instead. Gate the compressed cache inode case on COMPRESS_CACHE, matching f2fs_init_compress_inode(). With compress_cache disabled, ino == max_nid now follows the normal inode path and is rejected as an out-of-range nid.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.14
- Fix · CNA Linux (Linux) Fixed in 5.15.212, 6.1.177, 6.6.144, 6.12.95, 6.18.38, 7.1.3, 7.2
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2026-63817
- 2026-10-03 Alias added: GHSA-cv79-fx5q-34h3
- 2026-10-20 Affected versions changed · Red Hat
References
Other 7
- https://git.kernel.org/stable/c/fcc051d377a9701a452e7663a1a8223c26225df9
- https://git.kernel.org/stable/c/29115b8c9172d34e67ab26cc4f6c209b7a236d7a
- https://git.kernel.org/stable/c/13e4b59d3a9413f66f116fa6c4828519b960a5ea
- https://git.kernel.org/stable/c/16161444c30d8dff9428abbae42b72ce4e32a932
- https://git.kernel.org/stable/c/77f216ff9ce5cde8eed9f6d12707e906dffdc9f7
- https://git.kernel.org/stable/c/0969926d987bbde9a1aa49da317582ba37095805
- https://git.kernel.org/stable/c/5073c66a96a9c23c0c2533ed4ed06e42f9021208
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Sources
- CVE-2026-63817 · CVE Program
- CVE-2026-63817 · NVD
- FIRST EPSS
- GHSA-cv79-fx5q-34h3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-63817 · Red Hat security data · CC BY 4.0
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