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CVE-2021-27953

24
FAUCET Score

CVE-2021-27953 is a NULL pointer dereference vulnerability affecting ecobee3 lite devices running firmware version 4.5.81.200 during the HomeKit Wireless Access Control setup. An unauthenticated attacker can exploit this by sending a crafted HTTP request, leading to a denial of service and device reboot. With a CVSS score of 7.5 (HIGH), this vulnerability is easily exploitable over the network with low complexity and no user interaction, resulting in high availability impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

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

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.67%
Probability of exploitation in next 30 days
EPSS Percentile
74.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0167 is in the 57th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 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/remote-denial-of-service-of-ecobee3-lite
ExploitThird Party Advisory