CVE-2026-53182: Linux Kernel nl80211 Wi-Fi RNR Buffer Validation Vulnerability

Technical summary

The vulnerability resides in nl80211_parse_rnr_elems(), which parses nested NL80211_ATTR_EMA_RNR_ELEMS attributes from user-supplied input. The function stores element counts in a u8-backed cfg80211_rnr_elems::cnt field, creating a 255-item ceiling. The parser does not reject input once cnt reaches 255 before attempting the next increment, allowing the count to wrap or the flexible array member (FAM) allocation to size based on an incorrect count. The patch adds a bounds check that rejects further input once cnt reaches 255, matching the existing validation pattern in nl80211_parse_mbssid_elems(). This prevents allocation of a FAM with a size misaligned from the actual element count.

Business impact

This vulnerability could allow a local, authenticated attacker to cause a kernel memory corruption event, leading to privilege escalation or denial of service. Organizations running vulnerable kernel versions on systems with Wi-Fi drivers enabled are at risk. The impact is limited to local attack vectors, requiring the attacker to have user-level access on the target system. Widespread availability of patches and the need for local access reduce immediate risk, but systems in shared computing environments or with permissive local user policies warrant prioritization.

Affected systems

The Linux kernel is affected across all versions prior to the patch. The vulnerability is specific to kernel configurations with Wi-Fi (nl80211) subsystem support enabled. Affected systems include Linux distributions running standard or custom kernels with Wi-Fi networking functionality. Check your kernel version against your distribution's security advisories for exact patched versions.

Exploitability

This vulnerability requires local code execution and authentication to exploit. It is not remotely exploitable over a network. An attacker must either already have user-level access or be able to interact with the kernel's nl80211 interface via a local process. Public exploit code has not been reported, and the CVSS vector does not indicate active exploitation in the wild. However, the fix is straightforward, suggesting researchers and attackers alike understand the flaw clearly.

Remediation

Apply a kernel update from your Linux distribution that includes the patch to nl80211_parse_rnr_elems(). Verify the patch commit or security advisory from your vendor (e.g., Red Hat, Ubuntu, Debian, SUSE) to confirm the fix is included. If a kernel update cannot be deployed immediately, restrict local user access to systems with Wi-Fi subsystem functionality or disable Wi-Fi drivers if not required. Monitor for suspicious kernel memory errors or unexpected privilege escalations on affected systems.

Patch guidance

Contact your Linux distribution vendor for the patched kernel version. Canonical (Ubuntu), Red Hat, Debian, SUSE, and other major distributors will issue security updates. Test kernel updates in a non-production environment first, as they require a system reboot. Prioritize systems that run user-facing services or permit non-administrative local user accounts. Kernel updates are typically applied via package managers (apt, yum, zypper) followed by a reboot.

Detection guidance

Monitor kernel logs for memory corruption or allocation failures related to nl80211 or Wi-Fi configuration parsing. Look for segmentation faults, kernel panics, or memory sanitizer (KASAN) reports tied to the Wi-Fi subsystem. If SELinux or AppArmor is enabled, audit logs may capture attempts to manipulate Wi-Fi configuration attributes. Intrusion detection systems with kernel-level visibility can flag abnormal nl80211 attribute parsing patterns, though this requires custom rule development. Runtime kernel monitoring (e.g., via eBPF tools) may detect oversized RNR list injection attempts.

Why prioritize this

Assign this a HIGH priority for systems where local user access is common or least privilege is not enforced. Kernel privilege escalation vulnerabilities in frequently used subsystems like Wi-Fi merit rapid patching. However, organizations with strong access controls and no local user accounts may deprioritize slightly. The CVSS score of 7.8 reflects confidentiality, integrity, and availability impacts, justifying urgent remediation within standard SLA windows (typically 7–14 days for critical infrastructure, 30 days for general enterprise).

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) is driven by the attack vector being local (AV:L), low attack complexity (AC:L), low privileges required (PR:L), no user interaction (UI:N), and impact across all three pillars: confidentiality (C:H), integrity (I:H), and availability (A:H). The score reflects the severity of privilege escalation and memory corruption possible via a bounds-checking bypass. The fact that exploitation requires local access and authentication prevents a CRITICAL score, but the breadth of potential impact warrants urgent attention.

Frequently asked questions