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

Official 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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/785df00bb3ae3206674a43284eb06dac575b5c64
• https://git.kernel.org/stable/c/2c1ad291f4cdc357f9527b688c6fda9c6ffa7890
• https://git.kernel.org/stable/c/dd26d30f40c43ad9cfe2f25c6ea0ead1dd51d5aa
• https://git.kernel.org/stable/c/9635507fe82949e429b3cd938876a9917125b151
• https://git.kernel.org/stable/c/0f344944c506b4f02d2b098489f7268b438c369e
• https://git.kernel.org/stable/c/bfcca5f42c9aa4eadef1e5fe7bb23783d7fcc96d
• https://git.kernel.org/stable/c/304f5b414f4051d324b8c4a3ab0e79f7dc7e150e
• https://git.kernel.org/stable/c/f33cecf69095c43be88567fef92b180b858f7369
• https://git.kernel.org/stable/c/5cdcca5d62a66eda6b774110a44cba67bc1a8d1d