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

> A proximity attacker can trigger an out-of-bounds read in the Linux kernel NFC driver to disclose kernel memory or cause a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-99561, BELL-CVE-2026-80823, DEBIAN-CVE-2026-80823, GHSA-vwx2-rh9p-3f2w, UBUNTU-CVE-2026-80823

## What is CVE-2026-80823?

CVE-2026-80823 is a vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### 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.

## Which versions are affected by CVE-2026-80823?


## How do I fix CVE-2026-80823?

Apply the vendor's patch.

## Is CVE-2026-80823 being exploited?

There is no known exploitation of CVE-2026-80823 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80823 and fix it if it is affected.

What it is: CVE-2026-80823 is a vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80823 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80823/ (Markdown: https://insights.sbomify.com/CVE-2026-80823/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80823
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80823
- OSV: https://osv.dev/vulnerability/CVE-2026-80823

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80823/
Summaries are generated and may contain mistakes; the official description above is the record.