Bug 2457830 (CVE-2026-31414)

Summary: CVE-2026-31414 kernel: Linux kernel (netfilter): Denial of Service via unsafe connection tracking helper operations
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's netfilter component. This vulnerability allows a local attacker with low privileges to cause a denial of service (DoS). The issue arises from the improper handling of network connection tracking expectations, where a helper function was used unsafely without the necessary safeguards. This could lead to system instability or unresponsiveness.
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Description OSIDB Bzimport 2026-04-13 14:01:53 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_expect: use expect->helper

Use expect->helper in ctnetlink and /proc to dump the helper name.
Using nfct_help() without holding a reference to the master conntrack
is unsafe.

Use exp->master->helper in ctnetlink path if userspace does not provide
an explicit helper when creating an expectation to retain the existing
behaviour. The ctnetlink expectation path holds the reference on the
master conntrack and nf_conntrack_expect lock and the nfnetlink glue
path refers to the master ct that is attached to the skb.
Comment 1 Alexander B 2026-04-14 10:24:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026041308-CVE-2026-31414-90e7@gregkh/T