VulnerabilityPublished 17 Sep 2026Updated 5 Oct 2026

CVE-2026-93100: Linux kernel · fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-93100

Not known to be exploited.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 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.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix has been implemented that synchronizes the reference count decrement with a mutex to prevent the race condition causing use-after-free. Users should apply the official patches or updates provided by their Linux distribution or vendor for the affected Linux Azure kernel versions. Since this is a kernel-level issue, updating to a fixed kernel version is the recommended remediation.

Description

A use-after-free vulnerability in the Linux kernel's resctrl filesystem was resolved. The issue occurs in the rdtgroup_kn_put() function where a struct rdtgroup may be freed concurrently by two different code paths, leading to potential use-after-free and double free conditions. The fix involves synchronizing the decrement of the reference count with a mutex to prevent concurrent freeing. This vulnerability affects specific Linux Azure kernel versions and has a medium severity rating.

Impact

This vulnerability can lead to use-after-free and double free conditions in the Linux kernel's resctrl filesystem, potentially causing kernel crashes or undefined behavior. No known exploits in the wild have been reported. The impact is limited to affected Linux Azure kernel versions.

Summary

The Linux kernel's resctrl filesystem contained a use-after-free vulnerability in the rdtgroup_kn_put() function. The struct rdtgroup is reference counted via waitcount, and callers use rdtgroup_kn_get() and rdtgroup_kn_put() to manage references. The release path in rdtgroup_kn_put() serves as a fallback free operation if the count drops to zero and the group is marked RDT_DELETED. However, bulk teardown functions free_all_child_rdtgrp() and rmdir_all_sub() also free rdtgroup structures while holding a mutex. A race condition exists because rdtgroup_kn_put() decrements the count outside the mutex and then reads flags, allowing a concurrent bulk free to free the structure before the flags are read, causing use-after-free and potential double free. The fix replaces atomic_dec_and_test() with atomic_dec_and_mutex_lock() to ensure the decrement-to-zero operation holds the mutex, making the two free paths mutually exclusive. Additional adjustments defer kernfs_unbreak_active_protection() until after the mutex is dropped to avoid deadlocks.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-93100
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:Pro:14.04:LTS, Ubuntu:Pro:16.04:LTS, Ubuntu:16.04:LTS, Ubuntu:Pro:18.04:LTS, Ubuntu:18.04:LTS, Ubuntu:Pro:FIPS-updates:18.04:LTS, Ubuntu:Pro:FIPS:18.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:FIPS-updates:20.04:LTS, Ubuntu:Pro:FIPS:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:26.04:LTS

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 23:42 UTC

Technical details

References

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