wifi: at76c50x-usb: avoid length underflow in at76_guess_freq()

In the Linux kernel, the following vulnerability has been resolved: wifi: at76c50x-usb: avoid length underflow in at76_guess_freq() at76_guess_freq() checks only that the received frame is at least a bare 802.11 header (24 bytes) before subtracting the fixed management-body offset: len -= el_off; For both beacon and probe response frames, el_off is 36. If the frame is shorter than el_off, subtracting it causes the calculated IE length to wrap. The length is eventually passed to cfg80211_find_elem_match() as a very large unsigned value, so the element walk runs beyond the RX skb. This path is reached from at76_rx_tasklet() while scanning. If the device delivers a truncated beacon or probe response, the oversized IE length causes an out-of-bounds read during scanning. Skip the IE lookup if the frame does not reach the variable elements, before subtracting el_off.

Source published

10 Aug 2026 12:03:51 UTC

Source modified

19 Oct 2026 21:09:06 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 8.1 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H