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CVE-2021-27952

29
FAUCET Score

CVE-2021-27952 describes a critical vulnerability in the ecobee3 lite smart thermostat (firmware 4.5.81.200) due to hardcoded default root credentials. An attacker can exploit this by gaining access to the serial console, bypassing the bootloader's password protection. This vulnerability carries a CVSS score of 9.8 (Critical), indicating a severe risk with network-based attacks, low complexity, and complete compromise of confidentiality, integrity, and availability. While no active exploitation, public exploit code, or significant community discussion has been observed, the presence of hardcoded credentials (CWE-798) presents a significant security flaw.

Impacted Technologies

VendorProductVersion(s)CPE
4.5.81.200CPE matchmatch criteria
cpe:2.3:o:ecobee:ecobee3_lite_firmware:4.5.81.200:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.13%
Probability of exploitation in next 30 days
EPSS Percentile
63.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0113 is in the 49th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

l9group.com / advisories/hard-coded-default-root-credentials-for-all-ecobee3-lite-devices
ExploitThird Party Advisory