# CVE-2026-98921: Linux kernel use-after-free in overlayfs debug print

Source: https://junglewise.ai/threats/cve-2026-98921-in-the-linux-kernel-the-following-vulnerability-has-been-resolved  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-98921 · Severity: info · Published 2026-10-23

The Linux kernel's overlayfs filesystem contains a use-after-free bug in debug output code that can crash the system when CONFIG_OVERLAY_FS_DEBUG is enabled. The vulnerability only affects systems with debug mode on and causes a kernel panic rather than data exposure or privilege escalation.

Technologies: [Linux kernel](https://junglewise.ai/threats/technologies/x-linux-kernel).

## Quick answers

**Is CVE-2026-98921 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-98921 being exploited in the wild.

**How severe is CVE-2026-98921?** Informational severity, published 23 October 2026.

**Which products and versions are affected?** Linux kernel affected versions with CONFIG_OVERLAY_FS_DEBUG enabled.

**Is there a fix for CVE-2026-98921?** Yes: fixed in Fixed in commit ae146bc1abdeb4607abf2975b858c053024e8ac1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-98921 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-98921?** Check whether you run Linux kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Fixed in commit ae146bc1abdeb4607abf2975b858c053024e8ac1

## Technical details

The ovl_do_mkdir() function in overlayfs prints a dentry pointer after calling vfs_mkdir(), but vfs_mkdir() may free or replace that dentry on failure or success. The debug print accesses freed memory, triggering a use-after-free when CONFIG_OVERLAY_FS_DEBUG is enabled. The fix moves the dentry print before the vfs_mkdir() call.

## Affected products

- Linux kernel affected versions with CONFIG_OVERLAY_FS_DEBUG enabled

## Timeline

- 2026-10-23: disclosed: Published as CVE-2026-98921
- 2026-09-25: patched

## References

- [https://git.kernel.org/stable/c/719bd33ab359c539a68a278c15a97deb77565cdb](https://git.kernel.org/stable/c/719bd33ab359c539a68a278c15a97deb77565cdb)
- [https://git.kernel.org/stable/c/ae146bc1abdeb4607abf2975b858c053024e8ac1](https://git.kernel.org/stable/c/ae146bc1abdeb4607abf2975b858c053024e8ac1)

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