HOMEVULNERABILITIESCVE-2021-27952
CRITICAL

CVE-2021-27952

CWE-798Published: August 3, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

Hardcoded default root credentials exist on the ecobee3 lite 4.5.81.200 device. This allows a threat actor to gain access to the password-protected bootloader environment through the serial console.

NVD Source

Technical Analysis

CVE-2021-27952 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

ecobee2 product(s)
ecobee3 lite firmwareecobee3 lite
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://www.l9group.com/advisories/hard-coded-default-root-credentials-for-all-ecobee3-lite-devices
ADVISORYhttps://www.l9group.com/advisories/hard-coded-default-root-credentials-for-all-ecobee3-lite-devices

All References (2)

→
https://www.l9group.com/advisories/hard-coded-default-root-credentials-for-all-ecobee3-lite-devicesExploit · Third Party Advisory
→
https://www.l9group.com/advisories/hard-coded-default-root-credentials-for-all-ecobee3-lite-devicesExploit · Third Party Advisory

Quick Facts

CVE IDCVE-2021-27952
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-798
CISA KEVNo
Affected1 vendor(s)
PublishedAug 3, 2021

Related CVEs (CWE-798)

CVE-2026-13768
10.0
CVE-2025-42890
10.0
CVE-2026-22769
KEV10.0
CVE-2026-45631
10.0
CVE-2012-6428
10.0
CVE-2021-0248
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-27952 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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