# CVE-2026-93783: Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame

> A missing length check in the Linux kernel Bluetooth RFCOMM handler allows attackers to trigger out-of-bounds reads and potential crashes via malformed frames.

- **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:** 24 Sep 2026
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-103928, BELL-CVE-2026-93783, DEBIAN-CVE-2026-93783, GHSA-xv96-c36m-qhm7, UBUNTU-CVE-2026-93783

## What is CVE-2026-93783?

CVE-2026-93783 is a memory corruption vulnerability in Linux, published on 24 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:

Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame

rfcomm_recv_frame() casts skb->data to struct rfcomm_hdr and dereferences
hdr->addr and hdr->ctrl without validating skb->len first. A truncated
frame with skb->len less than the minimum header size causes an
out-of-bounds read of uninitialized memory. Additionally, a zero-length
frame causes skb->len-- to underflow to UINT_MAX, making
skb_tail_pointer() read far past the buffer.

Commit 23882b828c3c ("Bluetooth: RFCOMM: validate skb length in MCC
handlers") fixed the same class of missing-length-check bugs in the MCC
sub-handlers, but the top-level rfcomm_recv_frame() was left unfixed.
KMSAN reports:

  BUG: KMSAN: uninit-value in rfcomm_run
  ...
  Uninit was created at:
    __alloc_skb+0x474/0xb60
    vhci_write+0xe9/0x870

Fix this by rejecting frames smaller than sizeof(struct rfcomm_hdr) + 1
(the minimum frame must have a 3-byte header and a 1-byte FCS).

## Which versions are affected by CVE-2026-93783?


## How do I fix CVE-2026-93783?

Apply the vendor's patch.

## Is CVE-2026-93783 being exploited?

There is no known exploitation of CVE-2026-93783 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93783 and fix it if it is affected.

What it is: CVE-2026-93783 is a memory corruption vulnerability in Linux, published on 24 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-2026-93783 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-2026-93783/ (Markdown: https://insights.sbomify.com/CVE-2026-93783/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93783
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93783
- OSV: https://osv.dev/vulnerability/CVE-2026-93783

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93783/
Summaries are generated and may contain mistakes; the official description above is the record.