# CVE-2023-1901: HCI send_sync Dangling Semaphore Reference Re-use

> A malicious Bluetooth controller can exploit a dangling semaphore reference in the Zephyr RTOS HCI host layer to cause a crash or execute arbitrary code.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Jul 2023
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-xvvm-8mcm-9cq3

## What is CVE-2023-1901?

CVE-2023-1901 is a medium-severity use after free vulnerability in Zephyrproject Zephyr, published on 10 Jul 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The bluetooth HCI host layer logic not clearing a global reference to a semaphore after synchronously sending HCI commands may allow a malicious HCI Controller to cause the use of a dangling reference in the host layer, leading to a crash (DoS) or potential RCE on the Host layer.

Weakness: CWE-787 (Out-of-bounds Write), CWE-672 (Operation on a Resource after Expiration or Release)

## Which versions are affected by CVE-2023-1901?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2023-1901?

No fix has been published for CVE-2023-1901 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-1901 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-1901 exists.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2026-5067](https://insights.sbomify.com/CVE-2026-5067/): Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key (critical 9.8)
- [CVE-2022-3806](https://insights.sbomify.com/CVE-2022-3806/): Bluetooth HCI Error Handling Double Free (critical 9.8)
- [CVE-2017-14199](https://insights.sbomify.com/CVE-2017-14199/): Memory corruption in getaddrinfo (critical 9.8)
- [CVE-2018-1000800](https://insights.sbomify.com/CVE-2018-1000800/): Null dereference in n/a (critical 9.8)
- [CVE-2021-3329](https://insights.sbomify.com/CVE-2021-3329/): DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-1901 and fix it if it is affected.

What it is: CVE-2023-1901 is a medium-severity use after free vulnerability in Zephyrproject Zephyr, published on 10 Jul 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-1901 exists.

Affected product: Zephyrproject Zephyr. 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-2023-1901/ (Markdown: https://insights.sbomify.com/CVE-2023-1901/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-1901
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-1901
- OSV: https://osv.dev/vulnerability/CVE-2023-1901

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From sbomify Insights: https://insights.sbomify.com/CVE-2023-1901/
Summaries are generated and may contain mistakes; the official description above is the record.