CVE-2025-8300 Overview
CVE-2025-8300 is a heap-based buffer overflow [CWE-122] in the Realtek rtl81xx SDK Wi-Fi driver (rtwlanu) for Windows. The flaw resides in the N6CSet_DOT11_CIPHER_DEFAULT_KEY function, which fails to validate the length of user-supplied data before copying it into a fixed-length heap buffer. A local attacker with the ability to execute low-privileged code on the target system can exploit the flaw to escalate privileges and run arbitrary code in the context of SYSTEM. The issue was reported through the Zero Day Initiative as ZDI-CAN-26552 and disclosed publicly as ZDI-25-883.
Critical Impact
Successful exploitation yields arbitrary code execution as SYSTEM on Windows hosts running the affected Realtek Wi-Fi USB driver, giving attackers full control of the endpoint.
Affected Products
- Realtek Wi-Fi USB Driver on Windows
- Realtek RTL8811AU wireless hardware
- Systems using the Realtek rtl81xx SDK Wi-Fi driver (rtwlanu)
Discovery Timeline
- 2025-09-02 - CVE-2025-8300 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-8300
Vulnerability Analysis
The vulnerability is a heap-based buffer overflow in the rtwlanu component of the Realtek rtl81xx SDK Wi-Fi driver. The affected code path, N6CSet_DOT11_CIPHER_DEFAULT_KEY, copies attacker-controlled input into a fixed-size heap allocation without first checking the source length. Because the driver runs in kernel space, corrupting adjacent heap memory can be shaped into a controlled write primitive suitable for privilege escalation.
Exploitation requires local code execution as any user, including a low-privileged account. Once the attacker triggers the vulnerable IOCTL path exposed by the driver, oversized data overwrites structures in the kernel pool. Skilled attackers can leverage this corruption to hijack execution flow and run arbitrary code with SYSTEM privileges.
Root Cause
The root cause is missing input length validation in N6CSet_DOT11_CIPHER_DEFAULT_KEY prior to a copy operation into a fixed-length heap buffer. The function trusts the size or content of a caller-supplied cipher key parameter and performs the copy without bounds checking, producing a classic [CWE-122] heap overflow condition.
Attack Vector
The attack vector is local. An attacker first executes code on the target host under any user context, then opens a handle to the vulnerable Realtek driver device object and issues a crafted IOCTL request that reaches the N6CSet_DOT11_CIPHER_DEFAULT_KEY handler with an oversized payload. No user interaction is required beyond the attacker's initial foothold.
RealCodeExamples were not provided for this CVE. Refer to the Zero Day Initiative Advisory ZDI-25-883 for additional technical context.
Detection Methods for CVE-2025-8300
Indicators of Compromise
- Unexpected loading or reloading of the rtwlanu.sys driver on systems that did not recently update Wi-Fi drivers.
- Kernel bugchecks or pool corruption crashes referencing rtwlanu or Realtek Wi-Fi components.
- New processes spawned as NT AUTHORITY\SYSTEM from parents running under a standard user session shortly after Wi-Fi driver interaction.
Detection Strategies
- Monitor for DeviceIoControl calls from low-privileged processes to Realtek Wi-Fi driver device objects.
- Correlate driver crash telemetry (WER, Event ID 1001) with subsequent privilege escalation activity on the same host.
- Baseline installed versions of the Realtek Wi-Fi USB driver across the fleet and flag hosts running vulnerable versions.
Monitoring Recommendations
- Enable kernel-mode driver auditing and forward driver load events (Sysmon Event ID 6) to a central analytics platform.
- Track process lineage where a non-administrative user process is followed by unexpected SYSTEM-level child processes.
- Alert on newly installed or unsigned versions of rtwlanu.sys on managed endpoints.
How to Mitigate CVE-2025-8300
Immediate Actions Required
- Inventory endpoints for the presence of the Realtek Wi-Fi USB driver (rtwlanu.sys) and identify hosts using RTL8811AU or related rtl81xx chipsets.
- Restrict local logon and code execution rights on affected hosts to reduce the attacker population that can reach the vulnerable IOCTL.
- Monitor the Zero Day Initiative Advisory ZDI-25-883 and Realtek support channels for a fixed driver release.
Patch Information
At the time of publication, no vendor advisory URL was listed in the NVD entry for CVE-2025-8300. Organizations should track updates from Realtek and their hardware OEM (for example, laptop or Wi-Fi adapter manufacturer) for a driver revision that addresses the heap overflow in N6CSet_DOT11_CIPHER_DEFAULT_KEY. Deploy the updated driver package through standard endpoint management tooling once available.
Workarounds
- Remove or disable the Realtek Wi-Fi USB adapter and uninstall the rtwlanu driver on systems where Wi-Fi is not required.
- Enforce application allowlisting to prevent execution of untrusted binaries that could trigger the vulnerable IOCTL path.
- Use Windows Defender Application Control or similar driver blocklist mechanisms to restrict loading of vulnerable driver versions once a patched build is identified.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
