CVE-2026-53178: Linux Kernel Realtek WiFi Driver Integer Underflow (8.1 HIGH)

Technical summary

CVE-2026-53178 is an unsigned integer underflow vulnerability (CWE-191) in the Linux kernel's staging driver for Realtek rtl8723bs WiFi adapters, specifically in the rtw_mlme module. The flaw occurs when processing WiFi management frames with Information Elements (IE). The code subtracts fixed offsets from ie_length without first validating that ie_length is large enough to accommodate those subtractions. When ie_length is smaller than the offset value, the subtraction on an unsigned integer underflows, wrapping to a very large positive number. This corrupted value is then used in subsequent memory operations, leading to out-of-bounds access. An attacker can craft malicious WiFi frames to trigger this condition.

Business impact

Organizations relying on Linux systems with rtl8723bs WiFi adapters—particularly in IoT deployments, embedded systems, or edge computing scenarios—face a HIGH severity threat. Successful exploitation can result in either denial of service (system crash) or information disclosure. In enterprise environments, this could disrupt wireless connectivity for affected devices, compromise data confidentiality, or enable lateral movement if sensitive kernel memory is leaked. The attack requires network proximity but no authentication, making it a concern for any organization with vulnerable wireless hardware connected to untrusted or semi-trusted networks.

Affected systems

The Linux kernel is affected, particularly systems with Realtek RTL8723BS WiFi adapters. The rtl8723bs driver is commonly found in laptops, development boards (Raspberry Pi variants, Orange Pi, etc.), and IoT devices manufactured between roughly 2014–2022. Staging drivers are typically used on older or less-maintained hardware, suggesting legacy or specialized deployments. Verify your systems' WiFi chipset using `lspci` or `lsusb` and kernel version to determine exposure.

Exploitability

Exploitability is rated HIGH (CVSS score 8.1, attack vector adjacent network, no privileges required, no user interaction). An attacker positioned on the same network segment can send crafted WiFi management frames without authentication. The vulnerability is triggered at the driver level during normal frame processing, requiring no social engineering or user action. However, exploitation is confined to adjacent network attacks—an attacker cannot exploit this remotely over the Internet. Public exploit code is not yet known to exist, but the simplicity of the integer underflow condition (missing bounds check) and its presence in a widely-used staging driver suggest weaponization risk.

Remediation

Apply kernel security updates that add bounds checks before ie_length subtraction in the rtw_mlme module. This involves patching the staging driver code to validate ie_length >= required_offset before performing subtraction. Verify against the vendor advisory for specific kernel versions and patch releases. Alternatively, for legacy systems where patching is infeasible, disable or remove the rtl8723bs driver if the WiFi adapter is not essential, or isolate affected devices to trusted network segments only.

Patch guidance

Check your Linux distribution and kernel version against upstream Linux kernel security advisories for rtl8723bs fixes published after June 2026. Major distributions (Debian, Ubuntu, Red Hat, SUSE) will backport fixes to their supported kernel branches. On Debian/Ubuntu, use `apt update && apt upgrade` for patched kernels. On Red Hat-based systems, use `yum update` or `dnf update`. Verify the fix by confirming the kernel logs no longer show underflow-related warnings or by inspecting the rtw_mlme.c source for bounds-checking code. Reboot is required to apply kernel patches.

Detection guidance

Monitor for WiFi management frame anomalies using network intrusion detection systems (IDS) that inspect IEEE 802.11 traffic. Look for frames with suspiciously small IE length fields or malformed IE structures. On affected systems, enable kernel logging (dmesg) to watch for memory access warnings, out-of-bounds messages, or driver crash dumps. Host-based detection is difficult because the vulnerability manifests as a kernel-level memory error; however, system instability or unexpected WiFi driver resets may indicate exploitation attempts. Correlate WiFi adapter resets or kernel panics with nearby wireless probe activity during the relevant timeframe.

Why prioritize this

This vulnerability merits immediate attention due to its HIGH CVSS score (8.1), the combination of confidentiality and availability impact, and the lack of authentication requirements. Although the attack vector is adjacent-network-only, many organizations have legacy or embedded systems with Realtek adapters on corporate networks. The staging driver status suggests the affected hardware may be older and less frequently patched in practice. Prioritize patching systems that are both exposed to untrusted network segments and equipped with rtl8723bs adapters.

Risk score, explained

CVSS 3.1 score of 8.1 (HIGH) reflects: (1) Attack Vector = Adjacent Network (higher privilege to reach than remote, but still a realistic threat in shared networks), (2) Attack Complexity = Low (no special conditions required), (3) Privileges Required = None (attacker needs no prior access), (4) User Interaction = None (automatic trigger on receipt of frame), (5) Confidentiality Impact = High (memory disclosure possible), (6) Integrity Impact = None, (7) Availability Impact = High (crash/DoS). The absence of integrity impact (no code execution apparent) prevents a 9.0+ critical rating, but the dual impact on C and A keeps it firmly in HIGH territory.

Frequently asked questions