VulnerabilityPublished 13 Apr 2026Updated 5 Nov 2026

CVE-2026-31422: Linux kernel · net/sched: cls_flow: fix NULL pointer dereference on shared blocks

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in cc707a4fd4c3b6ab2722e06bc359aa010e13d408 : 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 cc707a4fd4c3b6ab2722e06bc359aa010e13d408, a208c3e1232997e9317887294c20008dfcb75449, 942813276edeb1741fa5b0a73471beb4e495fa08 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 13 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < cc707a4fd4c3b6ab2722e06bc359aa010e13d408	Fixed in cc707a4fd4c3b6ab2722e06bc359aa010e13d408
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < a208c3e1232997e9317887294c20008dfcb75449	Fixed in a208c3e1232997e9317887294c20008dfcb75449
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < 942813276edeb1741fa5b0a73471beb4e495fa08	Fixed in 942813276edeb1741fa5b0a73471beb4e495fa08
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < 415ea0c973c754b9f375225807810eb9045f4293	Fixed in 415ea0c973c754b9f375225807810eb9045f4293
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < 57f94ac7e953eece5ed4819605a18f3cdfc63dcc	Fixed in 57f94ac7e953eece5ed4819605a18f3cdfc63dcc
LinuxLinux	Affected ≥ 1abf272022cf1d18469405f47b4ec49c6a3125db, < 9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e	Fixed in 9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================

References

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