CVE-2026-53257: Linux Kernel WiFi cfg80211 Denial of Service Vulnerability

Technical summary

CVE-2026-53257 is a denial-of-service vulnerability in the Linux kernel's cfg80211 wireless subsystem. The issue arises from insufficient validation of High Efficiency (HE) and Extremely High Throughput (EHT) 802.11ax/802.11be capability and operational element consistency. When eht_cap is populated but eht_oper is absent, the kernel's mac80211 component can dereference invalid pointers or access uninitialized state, leading to a kernel panic. The fix enforces strict consistency checks at the cfg80211 layer before allowing such configurations to propagate to drivers and mac80211.

Business impact

This vulnerability presents a denial-of-service risk to Linux systems running modern WiFi hardware supporting EHT standards. An authenticated local attacker or unprivileged user with access to WiFi configuration interfaces could trigger a kernel crash, disrupting system availability and forcing a restart. For environments relying on WiFi-connected infrastructure, IoT devices, or edge computing nodes, this may cause service interruptions. The attack requires local access and does not compromise confidentiality or integrity, limiting the blast radius to availability.

Affected systems

The Linux kernel is affected across distributions and versions where EHT WiFi support is present. This principally impacts systems with modern WiFi hardware (Intel AX/BE, Qualcomm, Broadcom with EHT drivers) and userspace tools (iw, wpa_supplicant) that may attempt to set EHT capabilities. Systems using older WiFi standards (802.11ac or earlier) are not affected. Embedded systems, access points, and client devices running contemporary Linux distributions with EHT drivers are at risk.

Exploitability

Exploitation requires local access and user-level privileges on the target system. An attacker cannot exploit this remotely. The vulnerability is triggered through WiFi configuration APIs (netlink interface) accessible to unprivileged users, making it relatively straightforward to trigger once local access is gained. No special knowledge or complex sequence of steps is required beyond submitting malformed WiFi capability data. However, not in the CISA KEV catalog, indicating no known active exploitation in the wild at present.

Remediation

Apply kernel updates from your Linux distribution that include the cfg80211 consistency enforcement patch. Verification should be done against vendor advisories for your specific distribution (Ubuntu, Debian, Red Hat, etc.) to identify the exact kernel version or patch identifier that resolves CVE-2026-53257. For systems where immediate patching is infeasible, restrict non-root access to WiFi configuration interfaces via Linux capability controls or AppArmor/SELinux policies.

Patch guidance

Identify the kernel version running on affected systems using 'uname -r'. Check your distribution's security advisories for CVE-2026-53257 to obtain the patched kernel version. Most major distributions publish CVE tracking pages with links to update repositories. Once a patched kernel is available, schedule a maintenance window and perform a full kernel update via your distribution's package manager (apt, yum, zypper, etc.), followed by a system reboot. Verify the new kernel version post-reboot and confirm WiFi functionality is restored.

Detection guidance

Monitor kernel logs for WiFi-related crashes or panics mentioning cfg80211, eht_cap, or eht_oper. Use 'journalctl -u kernel' or examine /var/log/kern.log for 'kernel panic' or 'BUG:' messages with stack traces involving mac80211 or cfg80211. On intrusion detection systems, look for netlink-based configuration attempts from unprivileged processes targeting wireless capabilities. System uptime monitoring can detect unplanned reboots that may correlate with exploitation attempts.

Why prioritize this

Assign this vulnerability medium priority. While the CVSS score is 5.5 (medium severity) and local exploitation is required, any DoS vector affecting system availability warrants timely remediation, especially in production WiFi infrastructure. The consistency enforcement fix is a targeted, low-risk change with minimal performance or compatibility impact. Prioritize patching for systems where WiFi is a critical function (access points, edge servers, IoT gateways).

Risk score, explained

The CVSS:3.1 score of 5.5 reflects the vulnerability's profile: local attack vector, low attack complexity, low privileges required, no user interaction needed, but impact limited to availability (no confidentiality or integrity loss, no privilege escalation). The 'H' (high) impact on availability acknowledges the crash severity, while the absence of broader system compromise keeps the overall score in the medium band.

Frequently asked questions