Use-after-free in Linux kernel - CVE-2026-43027
Published: May 2, 2026
Vulnerability identifier: #VU128881
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-43027
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Linux Foundation
Affected software:
Linux kernel
Linux kernel
Detailed vulnerability description
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in nf_conntrack_helper_unregister and expectation handling in netfilter nf_conntrack_helper when unregistering a helper while stale expectations remain. A local user can trigger helper unregistration and subsequent expectation access to cause a denial of service.
The issue is triggered because expectations referencing the helper survive cleanup and are later dereferenced during expectation dumps or packet-driven conntrack initialization.
How to mitigate CVE-2026-43027
Install security update from vendor's repository.
Sources
- https://git.kernel.org/stable/c/2c16e4d64dd91227742dfe196a3e7b0568bef65a
- https://git.kernel.org/stable/c/2cf2737c85a2ba2b52024dafe68ffad2676f97be
- https://git.kernel.org/stable/c/504ba4168466c91210c45acdc332479cfd5f2da6
- https://git.kernel.org/stable/c/5cf28d5c8dcbbe8af6d3b145babe491906d7bad1
- https://git.kernel.org/stable/c/620f3d14c1ef51d425060a3056ad8dbae8f998a3
- https://git.kernel.org/stable/c/90bd7e8501349db3006d21fbc09df9ffcb172965
- https://git.kernel.org/stable/c/a242a9ae58aa46ff7dae51ce64150a93957abe65
- https://git.kernel.org/stable/c/dc1739eff48e34cc71d4e2f03715493fbcebd8af