Bug 2516348 (CVE-2026-72348)

Summary: CVE-2026-72348 kernel: netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's netfilter subsystem, specifically within ip6tables. A remote attacker could send specially crafted IPv6 packets with malformed extension headers. Due to improper length checks, these malformed packets might not be correctly identified and dropped by ip6tables rules. This could allow an attacker to bypass intended security filtering policies.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-15 06:07:47 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop

The ah, hbh and rt matches check that the fixed extension header is
present, then use the header length field to derive the advertised
extension header length for matching.

For the ah match, add the missing advertised-length check. For hbh
and rt, update the existing advertised-length checks. In all three
cases, set hotdrop to true before returning false when the advertised
extension header length exceeds the available skb data.

Returning false treats the packet as a rule mismatch. Set hotdrop to
true and drop malformed packets so they cannot bypass rules intended
to drop packets with these IPv6 extension headers.
Comment 1 Keith Grant 2026-08-19 13:44:11 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081511-CVE-2026-72348-e6e6@gregkh/T