---
id: "CVE-2026-98600"
kind: "vulnerability"
aliases: ["CVE-2026-98600"]
title: "Linux kernel: short RFCOMM frames can leak header bytes to Bluetooth applications"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bluetooth", "linux-kernel", "package", "self-hosted"]
not_affected_if: ["bluetooth-disabled"]
published_at: "2026-10-18T16:17:12+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:21:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98600", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: short RFCOMM frames can leak header bytes to Bluetooth applications

A malformed 4-byte RFCOMM frame with the extended-length bit clear is not rejected, so the kernel passes the unparsed 3-byte header on as application data or as a multiplexer control command. The sources do not say what an attacker can do beyond this, so the impact is unconfirmed.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update the Linux kernel to a release that includes the upstream RFCOMM fix (the commit that extends the length check in rfcomm_recv_frame()); exact fixed versions are not in the sources.

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98600

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: RFCOMM: Reject short EA=0 frames in rfcomm_recv_frame()

While rfcomm_recv_frame() verifies that skb->len is at least
sizeof(*hdr) + 1 (4 bytes: 3-byte header + 1-byte FCS), an RFCOMM frame
with an extended 2-byte length field (!__test_ea(hdr->len)) has a 4-byte
header plus a 1-byte FCS (5 bytes minimum, sizeof(*hdr) + 2).

When a 4-byte RFCOMM frame with EA == 0 arrives:
1. The initial skb->len < sizeof(*hdr) + 1 check passes (4 < 4 is false).
2. Trimming the FCS byte decrements skb->len to 3.
3. If __check_fcs() succeeds, skb_pull(skb, 4) fails (4 > 3) and returns
   NULL without advancing skb->data.
4. Because the return value of skb_pull() is ignored, the un-pulled
   3-byte struct rfcomm_hdr remains at skb->data and is either queued as
   application payload via rfcomm_recv_data() or parsed as a multiplexer
   control command via rfcomm_recv_mcc() on DLCI 0.

Fix this by extending the length check in rfcomm_recv_frame() to also
require skb->len >= sizeof(*hdr) + 2 when !__test_ea(hdr->len).

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_