CVE-2026-72003 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: cyw: fix heap overflow on a short auth frame
brcmf_notify_auth_frame_rx() takes the frame length from the firmware event and copies the frame body with the management header offset subtracted:
u32 mgmt_frame_len = e->datalen - sizeof(struct brcmf_rx_mgmt_data); ... memcpy(&mgmt_frame->u, frame, mgmt_frame_len - offsetof(struct ieee80211_mgmt, u));
The only length check is e->datalen >= sizeof(*rxframe), so mgmt_frame_len can be anything from 0 up. offsetof(struct ieee80211_mgmt, u) is 24. When mgmt_frame_len is below that, the subtraction wraps as an unsigned value to a huge length. The memcpy then runs far past the kzalloc'd buffer. A malicious or malfunctioning AP can make the frame short during the external SAE auth exchange, so this is a remotely triggered heap overflow.
Reject frames shorter than the management header offset before the copy.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in the Linux kernel's brcmfmac wireless driver represents a critical remote code execution risk stemming from an integer underflow during memory allocation and copying operations. The flaw resides specifically within the brcmf_notify_auth_frame_rx function, which processes authentication frames received from connected access points or other network entities. When handling these events, the driver calculates the length of the management frame by subtracting a fixed offset corresponding to the size of the receive structure header from the total data length provided in the firmware event. This calculation is performed using unsigned 32-bit integers, which introduces a classic arithmetic underflow condition if the source value is smaller than the subtraction operand.
The technical root cause lies in the insufficient validation of input lengths before performing critical memory operations. The existing check only verifies that the total data length from the firmware event meets or exceeds the size of the receive frame structure itself. However, it fails to account for the subsequent offset required to parse the actual management header fields. Specifically, the code subtracts offsetof(struct ieee80211_mgmt, u), which equals twenty-four bytes, from the calculated remaining length. If an attacker provides a short authentication frame where the data length is less than this offset, the unsigned arithmetic wraps around to produce a massive positive integer value rather than a negative error state. This erroneous large value is then passed directly into a memcpy operation intended to copy the frame body into a kernel heap buffer allocated via kzalloc.
This logic flaw results in a severe out-of-bounds write vulnerability on the kernel heap. Because the calculated length wraps around to near the maximum limit of a 32-bit unsigned integer, the subsequent memory copy attempts to transfer data far beyond the boundaries of the originally allocated buffer. This heap overflow allows for arbitrary read and write capabilities within kernel space when triggered by specific crafted inputs. The impact is particularly severe because this vulnerability can be exploited remotely during the external Simultaneous Authentication of Equals exchange process. An adversary controlling a malicious or malfunctioning access point can transmit specially constructed short authentication frames to trigger this condition, potentially leading to privilege escalation, system compromise, or denial of service through kernel panic due to memory corruption.
From a classification perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound and CWE-787 Out-of-bounds Write in the Common Weakness Enumeration framework. In terms of tactical execution within an attack lifecycle, it corresponds to ATT&CK technique T1203 Exploitation for Client Execution, as it involves exploiting a client-side component through network interaction. The exploitation vector is classified as Network with Low complexity and requires no user interaction beyond being associated with the malicious wireless network, making it highly dangerous in public or unsecured Wi-Fi environments where devices automatically connect to available networks.
Mitigation strategies primarily involve applying vendor-provided kernel patches that address this specific logic error by enforcing stricter input validation. The definitive fix involves rejecting any authentication frames whose data length is less than the required management header offset before attempting any memory allocation or copying operations. This ensures that the arithmetic subtraction never results in an underflow condition, thereby preventing the calculation of invalid buffer sizes. System administrators should ensure their Linux kernels are updated to versions containing this patch and consider implementing wireless intrusion detection systems capable of identifying anomalous frame lengths during authentication exchanges as a compensating control for unpatched endpoints.