In the Linux kernel, the following vulnerability has been resolved:
f2fs: validate compress cache inode only when enabled
F2FSCOMPRESSINO() uses NMI(sbi)->maxnid as the synthetic inode number for the compressed page cache inode. That inode only exists when the compress_cache mount option is enabled.
When compresscache is disabled, maxnid is outside the valid inode range. A corrupted directory entry that points to ino == maxnid should therefore be rejected by f2fschecknidrange(). However, ismetaino() currently treats F2FSCOMPRESSINO() as a meta inode unconditionally, so f2fsiget() bypasses doread_inode() and its nid range check, and instantiates a fake internal inode instead.
Gate the compressed cache inode case on COMPRESSCACHE, matching f2fsinitcompressinode(). With compresscache disabled, ino == maxnid now follows the normal inode path and is rejected as an out-of-range nid.
{
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63817.json",
"cna_assigner": "Linux"
}