VulnerabilityPublished 28 Oct 2026

CVE-2026-99180: Linux kernel · unicode: free the map after a grace period

Source GCVE Database

Authoritative record:CVE-2026-99180

Not known to be exploited · fixed in a96c5299bd7305eb984377681eb3222a57376405 : patch Linux kernel soon.

Data as of 28 Oct 2026, 13:42 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Patch: Available – fixed in a96c5299bd7305eb984377681eb3222a57376405, 6560c3d9a6925e3747d9ad8463e16010c31ba715, 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-vcmx-2wrh-m3mj

What to do

Upgrade Linux kernel to a96c5299bd7305eb984377681eb3222a57376405, 6560c3d9a6925e3747d9ad8463e16010c31ba715 or 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b886ee3e778ec2ad43e276fd378ab492cf6819b7, < a96c5299bd7305eb984377681eb3222a57376405	Fixed in a96c5299bd7305eb984377681eb3222a57376405
LinuxLinux	Affected ≥ b886ee3e778ec2ad43e276fd378ab492cf6819b7, < 6560c3d9a6925e3747d9ad8463e16010c31ba715	Fixed in 6560c3d9a6925e3747d9ad8463e16010c31ba715
LinuxLinux	Affected ≥ b886ee3e778ec2ad43e276fd378ab492cf6819b7, < 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8	Fixed in 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8
LinuxLinux	Affected =5.2	Fixed in–

AI-suggested

A fix is available that delays freeing the unicode map until after a grace period, preventing use-after-free during pathwalks. Users should apply the official Linux kernel update containing this fix when available. Until patched, avoid scenarios where mounts are dropped while pathwalks are active if possible.

Description

A use-after-free vulnerability exists in the Linux kernel's unicode map handling during pathwalk operations in RCU mode. Filesystems like ext4, f2fs, and tmpfs may read a freed unicode map if a lookup occurs while the last reference to a mount goes away. This race condition can cause kernel memory corruption detected by KASAN.

Impact

This vulnerability can cause kernel memory corruption due to use-after-free, potentially leading to system instability or crashes. It affects pathwalk operations in filesystems using unicode casefolding, such as ext4, f2fs, and tmpfs. No public exploits or in-the-wild exploitation are currently known.

Summary

The Linux kernel's unicode map used in generic_ci_d_hash() and generic_ci_d_compare() can be freed prematurely after the last reference to a mount is dropped, while pathwalks still hold an RCU read lock. This leads to use-after-free conditions when filesystems such as ext4, f2fs, and tmpfs access the unicode map during pathwalks. The flaw arises because the unicode map is freed immediately in ->put_super() without waiting for a grace period, causing potential memory corruption. The fix delays freeing the map until after a grace period, ensuring any ongoing pathwalks complete safely. Overlayfs usage remains correct as it holds references properly.

References

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