CVE-2025-39849

What it actually does

Missing bounds check on ssid->datalen in __cfg80211_connect_result() allows memcpy or similar operations to write beyond the 32-byte SSID buffer when datalen exceeds IEEE80211_MAX_SSID_LEN, causing adjacent kernel memory corruption.

Why it matters to the business

Local attackers on affected Linux kernels can corrupt kernel memory through Wi-Fi connection result handling, leading to crashes, data leaks, or privilege escalation on servers, desktops, and container hosts; high ecosystem prevalence increases exposure across distributions and cloud images.

How an attack unfolds

An attacker with local access supplies a crafted Wi-Fi connection result containing an SSID longer than 32 bytes; the kernel copies the oversized data without checking, overwriting adjacent structures and enabling arbitrary code execution or container escape as seen in related VMSCAPE and Container-Optimized OS campaigns.

How to fix it

Upgrade Linux kernel to version 6.1.151 or later; apply the commit 8e751d46336205abc259ed3990e850a9843fb649 in stable trees; rebuild and reboot all affected systems; prioritize hosts running Container-Optimized OS or exposed Wi-Fi drivers.

How to confirm the fix worked

Verify running kernel version is at or above 6.1.151; confirm the bounds check exists in __cfg80211_connect_result() via source inspection or kernel symbol diff; test with a synthetic oversized SSID connect result in a lab environment.

Typical attack path

1. Obtain local user or container access on a vulnerable kernel
2. Trigger or intercept a Wi-Fi connect result event with oversized SSID
3. Trigger the uncapped copy in __cfg80211_connect_result()
4. Use resulting memory corruption for privilege escalation or container breakout

How to detect it

Review kernel logs for oops or panic messages referencing cfg80211 or __cfg80211_connect_result with abnormal SSID lengths; inspect audit logs for unexpected Wi-Fi connect attempts; correlate with process creation following Wi-Fi events on systems known to be targeted by VMSCAPE-style campaigns.

What your security team should do

• Immediately inventory all Linux hosts and apply the 6.1.151 kernel update within the next maintenance window
• Prioritize Container-Optimized OS and cloud images due to listed threat actor activity
• Enable kernel lockdown and restrict local Wi-Fi configuration privileges until patched
• Monitor for post-patch stability issues in Wi-Fi drivers