HOMEVULNERABILITIESCVE-2021-27953
HIGH

CVE-2021-27953

CWE-476Published: August 3, 2021· Updated: Jun 17, 2026

7.5
CVSS v3.1

Official Description

A NULL pointer dereference vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HomeKit Wireless Access Control setup process. A threat actor can exploit this vulnerability to cause a denial of service, forcing the device to reboot via a crafted HTTP request.

NVD Source

Technical Analysis

CVE-2021-27953 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 availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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/remote-denial-of-service-of-ecobee3-lite
ADVISORYhttps://www.l9group.com/advisories/remote-denial-of-service-of-ecobee3-lite

All References (2)

→
https://www.l9group.com/advisories/remote-denial-of-service-of-ecobee3-liteExploit · Third Party Advisory
→
https://www.l9group.com/advisories/remote-denial-of-service-of-ecobee3-liteExploit · Third Party Advisory

Quick Facts

CVE IDCVE-2021-27953
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-476
CISA KEVNo
Affected1 vendor(s)
PublishedAug 3, 2021

Related CVEs (CWE-476)

CVE-2022-36648
10.0
CVE-2010-2495
10.0
CVE-2023-48697
9.8
CVE-2022-30592
9.8
CVE-2021-4236
9.8
CVE-2023-46427
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-27953 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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