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CVE-2026-63817

HIGHCVSS 7.8/10EPSS 0.13%

Last modified

CVE-2026-63817 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. 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. EPSS estimates a 0.13% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability
0.13%

3.3th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < fcc051d377a9701a452e7663a1a8223c26225df9; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 29115b8c9172d34e67ab26cc4f6c209b7a236d7a; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 13e4b59d3a9413f66f116fa6c4828519b960a5ea; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 16161444c30d8dff9428abbae42b72ce4e32a932; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 77f216ff9ce5cde8eed9f6d12707e906dffdc9f7; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 0969926d987bbde9a1aa49da317582ba37095805; >= 6ce19aff0b8cd386860855185c6cd79337fc4d2b, < 5073c66a96a9c23c0c2533ed4ed06e42f9021208; a23706426da9b611be5beae0f3faa260fb453b4e; >= 5.13.19, < 5.14
LinuxLinux5.14

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63817?
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.
How severe is CVE-2026-63817?
CVE-2026-63817 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.13% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63817?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST