VulnerabilityPublished 1 May 2026Updated 6 Nov 2026

CVE-2026-43027: Linux kernel · netfilter: nf_conntrack_helper: pass helper to expect cleanup

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in dc1739eff48e34cc71d4e2f03715493fbcebd8af : patch Linux kernel soon.

Data as of 6 Nov 2026, 16:32 UTC

Severity

High

Rated High by Threat Radar's AI analysis · 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, 2026-11-06.

Patch

Available – fixed in dc1739eff48e34cc71d4e2f03715493fbcebd8af, a242a9ae58aa46ff7dae51ce64150a93957abe65, 620f3d14c1ef51d425060a3056ad8dbae8f998a3 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 1 May 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 6 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 ≥ ac7b848390036dadd4351899d2a23748075916bd, < dc1739eff48e34cc71d4e2f03715493fbcebd8af	Fixed in dc1739eff48e34cc71d4e2f03715493fbcebd8af
LinuxLinux	Affected ≥ ac7b848390036dadd4351899d2a23748075916bd, < a242a9ae58aa46ff7dae51ce64150a93957abe65	Fixed in a242a9ae58aa46ff7dae51ce64150a93957abe65
LinuxLinux	Affected ≥ ac7b848390036dadd4351899d2a23748075916bd, < 620f3d14c1ef51d425060a3056ad8dbae8f998a3	Fixed in 620f3d14c1ef51d425060a3056ad8dbae8f998a3
LinuxLinux	Affected ≥ ac7b848390036dadd4351899d2a23748075916bd, < 504ba4168466c91210c45acdc332479cfd5f2da6	Fixed in 504ba4168466c91210c45acdc332479cfd5f2da6
LinuxLinux	Affected ≥ ac7b848390036dadd4351899d2a23748075916bd, < 90bd7e8501349db3006d21fbc09df9ffcb172965	Fixed in 90bd7e8501349db3006d21fbc09df9ffcb172965
LinuxLinux	Affected ≥ ac7b848390036dadd4351899d2a23748075916bd, < 5cf28d5c8dcbbe8af6d3b145babe491906d7bad1	Fixed in 5cf28d5c8dcbbe8af6d3b145babe491906d7bad1

AI-suggested

A fix is available in the Linux kernel as indicated by multiple fixed commit versions. Users should update their Linux kernel to a version that includes the fix identified by the listed commit hashes. No additional mitigation steps are required beyond applying the official patch.

Description

A use-after-free vulnerability exists in the Linux kernel's netfilter nf_conntrack_helper component. The issue occurs because nf_conntrack_helper_unregister() fails to pass the correct helper pointer during cleanup, causing expectations referencing the helper to survive and later dereference a freed helper object. This can lead to kernel memory corruption and potential instability.

Impact

The vulnerability can cause use-after-free memory corruption in the kernel, which may lead to system instability or crashes. While no public exploits or in-the-wild exploitation are known, the flaw allows dereferencing of freed memory in kernel space, posing a risk of privilege escalation or denial of service if exploited.

Summary

CVE-2026-43027 is a vulnerability in the Linux kernel's netfilter nf_conntrack_helper subsystem. The function nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy() to remove expectations associated with the helper being unregistered. However, it incorrectly passes NULL instead of the helper pointer as the data argument, preventing the proper matching and destruction of expectations. After unregister returns, the helper object is freed, but the surviving expectations still reference this freed object. Subsequent operations that access these expectations cause a use-after-free condition, leading to kernel memory corruption detected by KASAN. The fix involves passing the actual helper pointer to ensure expectations are properly destroyed before the helper is freed.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 16:32 UTC

Technical details

References

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