---
id: CVE-2026-80823
title: 'nfc: st21nfca: validate ATR_REQ length against the received frame'
summary: |-
  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_SI…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    785df00bb3ae3206674a43284eb06dac575b5c64
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    2c1ad291f4cdc357f9527b688c6fda9c6ffa7890
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    dd26d30f40c43ad9cfe2f25c6ea0ead1dd51d5aa
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    9635507fe82949e429b3cd938876a9917125b151
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    0f344944c506b4f02d2b098489f7268b438c369e
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    bfcca5f42c9aa4eadef1e5fe7bb23783d7fcc96d
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    304f5b414f4051d324b8c4a3ab0e79f7dc7e150e
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    f33cecf69095c43be88567fef92b180b858f7369
  - >-
    Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf <
    5cdcca5d62a66eda6b774110a44cba67bc1a8d1d
  - Linux 3.17
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:44:15.864Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80823'
references:
  - url: 'https://git.kernel.org/stable/c/785df00bb3ae3206674a43284eb06dac575b5c64'
  - url: 'https://git.kernel.org/stable/c/2c1ad291f4cdc357f9527b688c6fda9c6ffa7890'
  - url: 'https://git.kernel.org/stable/c/dd26d30f40c43ad9cfe2f25c6ea0ead1dd51d5aa'
  - url: 'https://git.kernel.org/stable/c/9635507fe82949e429b3cd938876a9917125b151'
  - url: 'https://git.kernel.org/stable/c/0f344944c506b4f02d2b098489f7268b438c369e'
  - url: 'https://git.kernel.org/stable/c/bfcca5f42c9aa4eadef1e5fe7bb23783d7fcc96d'
  - url: 'https://git.kernel.org/stable/c/304f5b414f4051d324b8c4a3ab0e79f7dc7e150e'
  - url: 'https://git.kernel.org/stable/c/f33cecf69095c43be88567fef92b180b858f7369'
  - url: 'https://git.kernel.org/stable/c/5cdcca5d62a66eda6b774110a44cba67bc1a8d1d'
tags:
  - cve.org
epss: 0.00243
epssPercentile: 0.14381
ingestedAt: '2026-10-19T09:16:01.504Z'
---

## Overview

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

- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 785df00bb3ae3206674a43284eb06dac575b5c64`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 2c1ad291f4cdc357f9527b688c6fda9c6ffa7890`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < dd26d30f40c43ad9cfe2f25c6ea0ead1dd51d5aa`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 9635507fe82949e429b3cd938876a9917125b151`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 0f344944c506b4f02d2b098489f7268b438c369e`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < bfcca5f42c9aa4eadef1e5fe7bb23783d7fcc96d`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 304f5b414f4051d324b8c4a3ab0e79f7dc7e150e`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < f33cecf69095c43be88567fef92b180b858f7369`
- `Linux >= 1892bf844ea0261736bd5e75546fc996e9daeedf < 5cdcca5d62a66eda6b774110a44cba67bc1a8d1d`
- `Linux 3.17`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.