CVE-2024-57898

What it actually does

Incorrect ordering during Wi-Fi link deletion clears the link ID from the valid_links bitmap before cleanup functions like cfg80211_cac_event() complete, triggering WARN_ON() when those functions require the ID to remain present.

Why it matters to the business

Wireless interface operations on affected Linux kernels can produce kernel warnings or instability during link management, potentially disrupting Wi-Fi connectivity or requiring reboots on servers, routers, and embedded devices.

How an attack unfolds

An attacker with local or adjacent network access triggers nl80211_remove_link followed by operations that invoke cfg80211_cac_event through the ieee80211 link teardown path, causing the early bitmap clear to hit the warning condition.

How to fix it

Update to a kernel containing commit ae07daf440d3220d0986e676317a5da66e4f9dfd or later; apply the corrected ordering that clears the link ID bitmap only after all cleanup completes. Reboot after kernel package upgrade.

How to confirm the fix worked

Confirm the patch is present by checking for the corrected sequence in cfg80211_remove_link; verify no WARN_ON occurs during link delete plus CAC event sequences in testing; inspect kernel version against the fixed commit.

Typical attack path

1. Obtain access to trigger Wi-Fi link management ioctls or netlink commands
2. Initiate link deletion via nl80211_remove_link while CAC or related events are pending
3. Force ieee80211_del_intf_link path to call functions expecting valid link ID
4. Observe WARN_ON or resulting kernel log entries and potential interface instability

How to detect it

Search kernel logs (dmesg, journalctl) for WARN_ON messages referencing cfg80211_cac_event or valid_links during link deletion; correlate with nl80211_remove_link calls in audit or system traces.

What your security team should do

• Prioritize kernel updates on all systems exposing Wi-Fi interfaces
• Monitor kernel logs for cfg80211 WARN_ON entries related to link deletion
• Test wireless link add/delete operations in staging environments before broad deployment
• Review downstream dependent packages for any additional backports needed