CVE-2026-93166 in Linux
Summary
by MITRE • 09/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: rtw89: debug: fix off by on in rtw89_ppdu_str()
This > comparison should be >= to avoid an out of bounds access.
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Analysis
by VulDB Data Team • 09/18/2026
The identified vulnerability resides within the Realtek RTW89 wireless driver subsystem of the Linux kernel, specifically affecting the debugging functionality implemented in the file related to PPDU (Physical Protocol Data Unit) string representation. The core technical flaw is a classic off-by-one error located inside the rtw89_ppdu_str() function. This routine is responsible for formatting and outputting detailed diagnostic information regarding wireless packet structures, which is critical for developers and system administrators troubleshooting connectivity or performance issues on devices utilizing this hardware driver.
The specific logical defect involves an incorrect boundary check condition where a greater-than operator was used instead of the required greater-than-or-equal-to operator when validating array indices against buffer sizes. In C programming, particularly within kernel space, such arithmetic errors can lead to severe memory safety violations. When the index reaches exactly the size of the allocated buffer or string limit, the flawed comparison allows the code to proceed with an access operation that exceeds the valid memory range. This results in a read-out-of-bounds condition, where the function attempts to retrieve data from a memory location immediately following the intended buffer boundary.
From a security perspective, this vulnerability is categorized under CWE-193, which defines off-by-one errors leading to out-of-bounds reads or writes depending on context. In this specific instance, since it involves reading string data for debugging output, it primarily constitutes an information disclosure risk rather than immediate code execution. However, the implications extend beyond simple data leakage. An attacker who can trigger this debug path through crafted wireless frames or by manipulating system states that invoke PPDU logging could potentially read sensitive kernel memory contents. This may include stack variables, pointers to other structures, or cryptographic keys if they reside in adjacent memory regions. Such information leaks facilitate further exploitation strategies and violate the principle of least privilege within the operating system's isolation boundaries.
The operational impact is primarily tied to the availability and integrity of diagnostic capabilities rather than direct service disruption under normal conditions. Since this code path is typically activated during debugging or verbose logging scenarios, it may not be reachable in production environments with default settings. Nevertheless, if a system administrator enables detailed wireless driver tracing for troubleshooting purposes, the vulnerability becomes active. The out-of-bounds read could cause kernel panics due to accessing unmapped memory pages, leading to local denial of service. Alternatively, it might result in corrupted log output that misleads administrators during incident response activities.
Mitigation strategies must address both immediate remediation and long-term defensive coding practices. The primary fix involves correcting the comparison operator within rtw89_ppdu_str() to ensure strict adherence to buffer boundaries by using a greater-than-or-equal-to check before any array access occurs. This aligns with secure coding standards that mandate explicit bounds checking for all dynamic memory accesses. Furthermore, developers should employ static analysis tools and fuzzing techniques during the development lifecycle to detect such arithmetic errors early. For system operators, ensuring that kernel updates are applied promptly is essential as this flaw has been resolved in upstream Linux repositories. Disabling unnecessary debug logging features on production systems also reduces the attack surface by preventing access to vulnerable code paths unless explicitly required for maintenance windows.
This vulnerability highlights the importance of rigorous validation in low-level driver development where memory safety is not guaranteed by language semantics like those found in higher-level managed languages. The ATT&CK framework does not have a direct technique for this specific kernel bug, but it relates broadly to techniques involving exploitation of software vulnerabilities and potential data exfiltration through memory corruption or leakage. Adhering to strict input validation protocols and utilizing compiler-based security features such as stack canaries and address space layout randomization provides additional layers of defense against the consequences of such logical flaws in system software components.