# CVE-2026-80800: nfc: llcp: bound the connect_sn TLV walk to the skb

> A nearby NFC attacker can trigger an out-of-bounds read in the Linux kernel LLCP parser, potentially causing a crash or leaking memory.

- **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-99596, BELL-CVE-2026-80800, DEBIAN-CVE-2026-80800, GHSA-8pjc-rhhp-w5xq, UBUNTU-CVE-2026-80800

## What is CVE-2026-80800?

CVE-2026-80800 is a memory corruption 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: llcp: bound the connect_sn TLV walk to the skb

Commit 27256cdb290e ("nfc: llcp: bound SNL TLV parsing to the skb and
add length checks") fixed the unbounded TLV walk in nfc_llcp_recv_snl(),
and commit d8bd2dedbde5 ("nfc: llcp: fix OOB read and u8 offset wrap in
TLV parsers") subsequently bounded nfc_llcp_parse_gb_tlv() and
nfc_llcp_parse_connection_tlv(). One sibling parser sharing the same
pattern remains unbounded: nfc_llcp_connect_sn().

nfc_llcp_connect_sn() walks a TLV list, reading a two-byte header
(type, length) followed by length bytes of value, without checking that
the two header bytes or the declared length stay within the buffer. It
returns a pointer to a service name of up to 255 bytes that may point
past the end of the skb; it is subsequently consumed by memcmp() in
nfc_llcp_sock_from_sn(). In addition tlv_array_len was computed as
"skb->len - LLCP_HEADER_SIZE" in size_t, so a CONNECT/CC frame shorter
than the LLCP header underflows to a huge length and the walk runs far
past the buffer.

nfc_llcp_connect_sn() is reachable from nfc_llcp_recv_connect() and
nfc_llcp_recv_cc(), i.e. from received CONNECT and CC PDUs. A nearby
NFC device can reach this without authentication; LLCP link activation
happens automatically after NFC-DEP, and the nfc_llcp_rx_skb()
dispatcher applies no minimum-length guard.

Walk the TLV list by pointer, bounded by skb_tail_pointer(skb), and
validate each declared length before use, matching the approach already
used for nfc_llcp_recv_snl(). Starting the walk at
&skb->data[LLCP_HEADER_SIZE] against the tail pointer also removes the
size_t underflow for short frames.

Found by 0sec automated security-research tooling (https://0sec.ai).

## Which versions are affected by CVE-2026-80800?


## How do I fix CVE-2026-80800?

Apply the vendor's patch.

## Is CVE-2026-80800 being exploited?

There is no known exploitation of CVE-2026-80800 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80800 and fix it if it is affected.

What it is: CVE-2026-80800 is a memory corruption 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-2026-80800 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-2026-80800/ (Markdown: https://insights.sbomify.com/CVE-2026-80800/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80800
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80800
- OSV: https://osv.dev/vulnerability/CVE-2026-80800

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80800/
Summaries are generated and may contain mistakes; the official description above is the record.