# CVE-2026-63817: linux: In the Linux kernel, the following vulnerability has been resolved:  f2fs: validate compress cache inode only when en...

CVE-2026-63817 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-63817, released July 20, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-63817
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 19, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.177-1 | [DEBIAN-CVE-2026-63817](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63817.md) | Jul 20, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.95-1 | [DEBIAN-CVE-2026-63817](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63817.md) | Jul 20, 2026 |
| Linux | linux Debian 14 | 7.1.3-1 | [DEBIAN-CVE-2026-63817](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63817.md) | Jul 20, 2026 |

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Data as of 2026-11-10T01:44:33Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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