CVE-2026-90017 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
staging: rtl8723bs: fix OOB read in rtw_action_frame_parse()
rtw_action_frame_parse() takes a frame_len parameter but never actually checks it before indexing into the frame body:
const u8 *frame_body = frame + sizeof(struct ieee80211_hdr_3addr); ... c = frame_body[0];
... a = frame_body[1];
frame_body already points 24 bytes (sizeof(struct ieee80211_hdr_3addr)) into frame, so reading frame_body[0] and
frame_body[1] requires frame_len >= 26. A management action frame
shorter than that (e.g. exactly 24 bytes, the minimum a malicious peer can send) causes a 1-2 byte out-of-bounds read.
This is reachable from rtw_cfg80211_monitor_if_xmit_entry() and cfg80211_rtw_mgmt_tx() in ioctl_cfg80211.c, both of which pass attacker/user-influenced frame buffers and lengths straight through.
Add the missing length check before frame_body is dereferenced.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel staging driver for the Realtek rtl8723bs wireless chipset contains a critical out-of-bounds read vulnerability within the rtw_action_frame_parse function, which poses significant risks to system stability and potential information disclosure. This flaw arises from an insufficient boundary check on user-supplied input data during the processing of IEEE 802.11 management action frames. The driver fails to validate that the provided frame length is sufficient before accessing specific indices within the frame body buffer, leading to memory access violations when malformed or truncated packets are processed by the network stack.
The technical root cause lies in the rtw_action_frame_parse function, which accepts a frame_len parameter representing the total size of the received wireless frame but neglects to verify this value against the required minimum length before dereferencing pointers into the payload. Specifically, the code calculates a pointer named frame_body by adding the size of an ieee80211_hdr_3addr structure, which is twenty-four bytes, to the base address of the frame buffer. Subsequent operations then read byte zero and byte one from this calculated offset using frame_body[0] and frame_body[1]. For these memory accesses to remain within valid bounds, the original frame_len must be at least twenty-six bytes. However, because no such validation exists, a malicious peer or local user can craft an action frame that is exactly twenty-four bytes long, which satisfies basic protocol expectations but falls short of the required payload size for safe parsing.
This vulnerability is exploitable through several entry points within the kernel's wireless configuration interface, specifically via rtw_cfg80211_monitor_if_xmit_entry and cfg80211_rtw_mgmt_tx located in ioctl_cfg80211.c. These functions act as intermediaries that pass frame buffers and their associated lengths directly to the vulnerable parsing routine without performing independent length verification. Consequently, an attacker capable of injecting wireless frames or manipulating local configuration ioctls can trigger this out-of-bounds read condition. The impact includes potential kernel panics due to invalid memory access, which results in a denial of service for the affected system. Furthermore, depending on the surrounding memory layout and compiler optimizations, reading beyond the allocated buffer boundaries may leak sensitive kernel stack or heap data into user space, facilitating information disclosure attacks that could aid further exploitation attempts against other security controls.
From a classification perspective, this vulnerability aligns with CWE-125, which describes out-of-bounds read errors where software reads memory past the end of a buffer. In terms of offensive cybersecurity frameworks such as MITRE ATT&CK, this flaw can be leveraged in techniques related to Discovery or Defense Evasion by causing system instability or extracting kernel information that may reveal internal structures and mitigations. The lack of input validation represents a fundamental failure in secure coding practices common in legacy staging drivers where rigorous testing is often less stringent than in mainline subsystems.
To mitigate this vulnerability, the primary remediation involves implementing strict length verification prior to any pointer arithmetic or array indexing operations within rtw_action_frame_parse. Developers must ensure that frame_len is explicitly checked against a minimum threshold of twenty-six bytes before calculating and dereferencing the frame_body pointer. This defensive programming practice ensures that only well-formed frames with sufficient payload data are processed, thereby preventing memory corruption and unauthorized access attempts. System administrators should apply kernel updates provided by their distribution vendors as soon as patches addressing this specific staging driver issue become available to restore secure operation of wireless networking components on affected systems.