# CVE-2024-1638: Bluetooth characteristic LESC security requirement not enforced without additional flags

> Attackers can read or write Bluetooth characteristics without encryption because the stack fails to enforce LE Secure Connections permissions unless additional flags are set.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Feb 2024
- **Updated:** 24 Apr 2025
- **Also known as:** GHSA-p6f3-f63q-5mc2

## What is CVE-2024-1638?

CVE-2024-1638 is a high-severity missing authorization vulnerability in Zephyrproject Zephyr, published on 19 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The documentation specifies that the BT_GATT_PERM_READ_LESC and BT_GATT_PERM_WRITE_LESC defines for a Bluetooth characteristic: Attribute read/write permission with LE Secure Connection encryption. If set, requires that LE Secure Connections is used for read/write access, however this is only true when it is combined with other permissions, namely BT_GATT_PERM_READ_ENCRYPT/BT_GATT_PERM_READ_AUTHEN (for read) or BT_GATT_PERM_WRITE_ENCRYPT/BT_GATT_PERM_WRITE_AUTHEN (for write), if these additional permissions are not set (even in secure connections only mode) then the stack does not perform any permission checks on these characteristics and they can be freely written/read.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2024-1638?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2024-1638?

No fix has been published for CVE-2024-1638 yet. Limit exposure of the affected software until one is available.

## Is CVE-2024-1638 being exploited?

There is no known exploitation of CVE-2024-1638 in the wild and no public exploit code.

## 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-2024-1638 and fix it if it is affected.

What it is: CVE-2024-1638 is a high-severity missing authorization vulnerability in Zephyrproject Zephyr, published on 19 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-1638 in the wild and no public exploit code.

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-2024-1638/ (Markdown: https://insights.sbomify.com/CVE-2024-1638/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-1638
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-1638
- OSV: https://osv.dev/vulnerability/CVE-2024-1638

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-1638/
Summaries are generated and may contain mistakes; the official description above is the record.