CVE-2021-27953

Exp

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.

Published: 2021-08-03 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-27953 is rated High Exploit Risk (71.2/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.67%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-27953

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-27953

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 1.26% 1.67% +0.42%
2 2025-11-21 0.97% 1.26% +0.28%
3 2025-11-18 — 0.97% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-27953

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.8 2.0 HIGH
AV:N/AC:L/Au:N/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 6.9 [email protected]

Weakness enumeration for CVE-2021-27953

Affected software / configurations for CVE-2021-27953

Vendor Product Version Raw CPE
ecobee ecobee3_lite_firmware 4.5.81.200 cpe:2.3:o:ecobee:ecobee3_lite_firmware:4.5.81.200:*:*:*:*:*:*:*

References for CVE-2021-27953

cvelogic Threat Intelligence