# CVE-2026-99180: Linux kernel unicode map use-after-free in path lookup

Source: https://junglewise.ai/threats/cve-2026-99180-in-the-linux-kernel-the-following-vulnerability-has-been-resolved  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-28. Updated: 2026-10-28  
License: CC BY 4.0 with a link back

CVE-2026-99180 · Severity: info · Published 2026-10-28

The Linux kernel's case-insensitive filename handling used by ext4, f2fs, and tmpfs contains a use-after-free vulnerability in the Unicode mapping tables. An attacker can trigger this by performing a directory lookup while simultaneously unmounting a filesystem, potentially leading to a kernel crash or information disclosure.

Technologies: [Linux Kernel](https://junglewise.ai/threats/technologies/kernel). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux).

## Quick answers

**Is CVE-2026-99180 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-99180 being exploited in the wild.

**How severe is CVE-2026-99180?** Informational severity, published 28 October 2026.

**Which products and versions are affected?** Linux Kernel Versions with CONFIG_UNICODE enabled using case-insensitive filename handling.

**Is there a fix for CVE-2026-99180?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-99180 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-99180?** 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.

## Technical details

The vulnerability occurs in generic_ci_d_hash() and generic_ci_d_compare() functions which dereference the Unicode map (sb->s_encoding) under RCU read lock. When a filesystem is unmounted via ->put_super(), the map is freed immediately even if an in-progress pathwalk is still reading it, causing a use-after-free. The fix delays map deallocation until after an RCU grace period expires, ensuring any active pathwalks complete before the memory is freed.</details>
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## Affected products

- Linux kernel Versions with CONFIG_UNICODE enabled using case-insensitive filename handling

## Timeline

- 2026-10-28: disclosed

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