CVE-2026-80823: nfc: st21nfca: validate ATR_REQ length against the received frame

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-04 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: nfc: st21nfca: validate ATR_REQ length against the received frame st21nfca_tm_recv_atr_req() checks that the received ATR_REQ frame is at least ST21NFCA_ATR_REQ_MIN_SIZE and that the self-declared atr_req->length is at least sizeof(struct st21nfca_atr_req), but never checks that atr_req->length does not exceed the actual received length (skb->len). st21nfca_tm_send_atr_res() then trusts the declared length: gb_len = atr_req->length - sizeof(struct st21nfca_atr_req); ... memcpy(atr_res->gbi, atr_req->gbi, gb_len); so an RF peer that sends a short frame but sets atr_req->length larger than the frame makes gb_len exceed the general bytes actually present, and the memcpy reads out of bounds past the received skb. Those bytes are placed in the ATR_RES and sent back to the peer (kernel-memory disclosure to a proximity attacker); a larger declared length is an out-of-bounds read (DoS). Reject frames whose declared length exceeds the received length. The adjacent nfc_tm_activated() path in the same function already derives its general-bytes length from skb->len rather than the declared field. Found by 0sec (https://0sec.ai) using automated source analysis; the missing bound is evident from source. Compile-tested.

Affected products

Linux kernel: 3.17 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

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