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CVE Record

CVE-2021-38545: Raspberry Pi 3 B+ and 4 B devices through 2021-08-09, in certain specific use cases in which the device sup...

Raspberry Pi 3 B+ and 4 B devices through 2021-08-09, in certain specific use cases in which the device supplies power to audio-output equipment, allow remote attackers to recover speech signals from an LED on the device, via a telescope and an electro-optical sensor, aka a "Glowworm" attack. We assume that the Raspberry Pi supplies power to some speakers. The power indicator LED of the Raspberry Pi is connected directly to the power line, as a result, the intensity of a device's power indicator LED is correlative to the power consumption. The sound played by the speakers affects the Raspberry Pi's power consumption and as a result is also correlative to the light intensity of the LED. By analyzing measurements obtained from an electro-optical sensor directed at the power indicator LED of the Raspberry Pi, we can recover the sound played by the speakers.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a physical side-channel privacy issue, not a typical software compromise. In narrow conditions, speech played through speakers powered by a Raspberry Pi 3 B+ or 4 B can be inferred by observing power LED brightness changes with optical sensing equipment.

Executive priority

Low for most organizations, but relevant for high-confidentiality rooms, labs, and embedded deployments where Raspberry Pi devices power speakers and are visually exposed.

Technical view

The CVE describes the "Glowworm" attack: the Raspberry Pi power indicator LED is tied to the power line, so speaker-driven power consumption can correlate with LED intensity. Measurements of the LED can be analyzed to recover speech signals when the Raspberry Pi supplies power to audio-output equipment.

Likely exposure

Exposure is likely limited to Raspberry Pi 3 B+ and 4 B devices through 2021-08-09 that power speakers, especially where the power LED is visible from an uncontrolled viewing position.

Exploitation context

No KEV listing or cited active exploitation evidence is provided. The attack requires specific hardware conditions, optical observation of the device LED, and analysis equipment, making broad opportunistic exploitation unlikely from the supplied evidence.

Researcher notes

The supplied CVE data lacks CVSS, CWE, CPE, patch details, and confirmed exploitation. Analysis should stay scoped to Raspberry Pi 3 B+ and 4 B through 2021-08-09 and the specific power-to-speaker use case.

Mitigation direction

  • Check Raspberry Pi or research guidance; no vendor patch is cited in the supplied sources.
  • Avoid using affected Raspberry Pi devices to power speakers in confidential areas.
  • Prevent uncontrolled visibility of power LEDs near sensitive audio environments.
  • Treat exposed device LEDs as a physical privacy risk during secure-room reviews.

Validation and detection

  • Inventory Raspberry Pi 3 B+ and 4 B devices in use.
  • Identify devices that supply power to audio-output equipment.
  • Confirm whether power indicator LEDs are visible outside controlled areas.
  • Review sensitive meeting or audio playback locations for this condition.
Prepared
Confidence
medium
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-38545 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.