CVE-2026-63817: Linux

High severity, CVSS 7.8. EPSS: 0.1% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux: from 5.13.19, before 5.14 (fixed in 5.14); from 5.14, before 5.15.212 (fixed in 5.15.212); from 5.16, before 6.1.177 (fixed in 6.1.177); from 6.2, before 6.6.144 (fixed in 6.6.144); from 6.7, before 6.12.95 (fixed in 6.12.95); from 6.13, before 6.18.38 (fixed in 6.18.38); …

Published 2026-07-19. Last modified 2026-08-17.