Bug 2492119 (CVE-2026-52915)

Summary: CVE-2026-52915 kernel: netfilter: ip6t_hbh: reject oversized option lists
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's netfilter subsystem, specifically within the ip6t_hbh module responsible for handling IPv6 Hop-by-Hop (HBH) options. This vulnerability allows a local attacker to provide an oversized list of HBH options from userspace, leading to an out-of-bounds write. This can result in memory corruption and potentially cause a system crash, leading to a denial of service.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-06-24 08:02:55 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: ip6t_hbh: reject oversized option lists

struct ip6t_opts stores at most IP6T_OPTS_OPTSNR option descriptors,
but hbh_mt6_check() does not reject larger optsnr values supplied from
userspace.

Validate optsnr in the rule setup path so only match data that fits the
fixed-size opts array can be installed. This follows the existing xtables
pattern of rejecting invalid user-provided counts in checkentry() and
keeps the packet matching path unchanged.

`struct ip6t_opts` has a fixed `opts[IP6T_OPTS_OPTSNR]` array,
where `IP6T_OPTS_OPTSNR` is 16, then off-by-one array access is possible:

[  137.924693][ T8692] UBSAN: array-index-out-of-bounds in ../net/ipv6/netfilter/ip6t_hbh.c:110:29
[  137.926167][ T8692] index 16 is out of range for type '__u16 [16]'
Comment 1 Mauro Matteo Cascella 2026-06-24 10:35:20 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062429-CVE-2026-52915-44dd@gregkh/T