VulnerabilityPublished 25 Sep 2026Updated 20 Oct 2026

CVE-2026-97938: Linux kernel · reboot: fix cad_pid use-after-free race

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-97938

Not known to be exploited.

Data as of 26 Oct 2026, 17:16 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 25 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.

ghsa-9x8r-8wjj-jgjv

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 is available that treats cad_pid as an RCU-protected pointer and waits for a grace period before dropping references, eliminating the use-after-free race. Users should apply the official Linux kernel updates that include this fix. Since this is a kernel vulnerability, upgrading to patched kernel versions is the recommended remediation. No additional mitigations are indicated by the vendor advisory.

Description

A use-after-free race condition in the Linux kernel's reboot subsystem involving the cad_pid pointer was resolved. The vulnerability arises because cad_pid, a kernel-wide struct pid pointer, was accessed without proper lifetime protection, allowing a concurrent writer to free the referenced struct pid while it was still in use. This could lead to kernel memory corruption. The issue was partially mitigated by moving cad_pid to the global reboot sysctl table but required further fixes to treat cad_pid as an RCU-protected pointer and properly synchronize reference dropping. The vulnerability affects specific Linux kernel versions and was fixed by implementing RCU protection and grace period waits on the pointer. No known exploits in the wild have been reported.

Impact

This vulnerability could lead to a use-after-free condition in the kernel, potentially causing kernel memory corruption or crashes. At the time of reporting, an unprivileged user could access the vulnerable sysctl through user and PID namespaces due to namespace and permission mismatches, increasing the risk of exploitation. However, no known exploits in the wild have been reported. The impact is considered medium severity due to the potential for kernel instability or denial of service.

Summary

The Linux kernel reboot subsystem had a use-after-free race condition involving the cad_pid pointer, a kernel-wide struct pid pointer. The function proc_do_cad_pid() reads cad_pid and passes it to pid_vnr() without protecting the lifetime of the referenced struct pid. Concurrent writes can replace cad_pid and drop the final reference to the old struct pid after the reader has loaded the pointer but before pid_vnr() finishes dereferencing it, causing a use-after-free. Similarly, kill_cad_pid() has the same race condition. Initially, moving cad_pid to the global reboot sysctl table corrected namespace and permission mismatches but did not fix the lifetime race. The final fix treats cad_pid as an RCU-protected pointer at both read sites and waits for a grace period before dropping the old reference on the write side. The fix avoids double queuing of the same RCU callback to prevent corruption. This vulnerability was resolved in the affected Linux kernel versions listed.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-97938
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:Pro:14.04:LTS, Ubuntu:Pro:16.04:LTS, Ubuntu:16.04:LTS, Ubuntu:Pro:FIPS: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

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 17:19 UTC

Technical details

References

Community reviews

Related threats