# CVE-2026-74508: Bluetooth: HIDP: reject frames without a transaction header

> A remote attacker can trigger use of uninitialized memory or terminate Bluetooth HID sessions by sending malformed L2CAP frames.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-96473, BELL-CVE-2026-74508, DEBIAN-CVE-2026-74508, GHSA-39c4-67x8-fp8m, UBUNTU-CVE-2026-74508

## What is CVE-2026-74508?

CVE-2026-74508 is a high-severity vulnerability in Linux, published on 15 Aug 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: HIDP: reject frames without a transaction header

hidp_recv_ctrl_frame() and hidp_recv_intr_frame() read skb->data[0]
before checking that the L2CAP SDU contains a transaction header. A
connected HIDP peer can send an empty basic-mode SDU and make both paths
use an uninitialized byte from skb tailroom.

KMSAN reports the use in hidp_session_run(), with the uninitialized value
originating in __alloc_skb() through vhci_write(). The control path
produces two reports and the interrupt path produces one.

The byte can also be controlled by a malformed lower-layer packet. If an
HCI ACL packet contains an L2CAP PDU with a declared zero-length payload
followed by an extra 0x15 byte, l2cap_recv_acldata() reduces skb->len to
the declared PDU length before dispatch. The current HIDP path nevertheless
consumes the extra byte as HIDP_TRANS_HID_CONTROL |
HIDP_CTRL_VIRTUAL_CABLE_UNPLUG and terminates the HIDP session. With this
change, the same packet is discarded and a subsequent feature report
request succeeds.

Pull the transaction header with skb_pull_data() and discard frames that
do not contain it.

## Which versions are affected by CVE-2026-74508?


## How do I fix CVE-2026-74508?

Apply the vendor's patch.

## Is CVE-2026-74508 being exploited?

There is no known exploitation of CVE-2026-74508 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74508 and fix it if it is affected.

What it is: CVE-2026-74508 is a high-severity vulnerability in Linux, published on 15 Aug 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-2026-74508 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-2026-74508/ (Markdown: https://insights.sbomify.com/CVE-2026-74508/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74508
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74508
- OSV: https://osv.dev/vulnerability/CVE-2026-74508

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74508/
Summaries are generated and may contain mistakes; the official description above is the record.