VulnerabilityPublished 3 Apr 2026Updated 5 Nov 2026

CVE-2026-23436: Linux kernel · net: shaper: protect from late creation of hierarchy

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in d22921727023e7852704965e935f4d1fc83a5ec9 : update Linux kernel when convenient.

Data as of 5 Nov 2026, 22:04 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-05.

Patch

Available – fixed in d22921727023e7852704965e935f4d1fc83a5ec9, d75ec7e8ba1979a1eb0b9211d94d749cdce849c8, 719f6784f918f9e32f3ff3b197f900e852223f9d

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 5 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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

Upgrade Linux kernel to d22921727023e7852704965e935f4d1fc83a5ec9, d75ec7e8ba1979a1eb0b9211d94d749cdce849c8 or 719f6784f918f9e32f3ff3b197f900e852223f9d.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 93954b40f6a4fc43226c01a15b02732f884500f1, < d22921727023e7852704965e935f4d1fc83a5ec9	Fixed in d22921727023e7852704965e935f4d1fc83a5ec9
LinuxLinux	Affected ≥ 93954b40f6a4fc43226c01a15b02732f884500f1, < d75ec7e8ba1979a1eb0b9211d94d749cdce849c8	Fixed in d75ec7e8ba1979a1eb0b9211d94d749cdce849c8
LinuxLinux	Affected ≥ 93954b40f6a4fc43226c01a15b02732f884500f1, < 719f6784f918f9e32f3ff3b197f900e852223f9d	Fixed in 719f6784f918f9e32f3ff3b197f900e852223f9d
LinuxLinux	Affected =6.13	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: net: shaper: protect from late creation of hierarchy We look up a netdev during prep of Netlink ops (pre- callbacks) and take a ref to it. Then later in the body of the callback we take its lock or RCU which are the actual protections. The netdev may get unregistered in between the time we take the ref and the time we lock it. We may allocate the hierarchy after flush has already run, which would lead to a leak. Take the instance lock in pre- already, this saves us from the race and removes the need for dedicated lock/unlock callbacks completely. After all, if there's any chance of write happening concurrently with the flush - we're back to leaking the hierarchy. We may take the lock for devices which don't support shapers but we're only dealing with SET operations here, not taking the lock would be optimizing for an error case.

References

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