PatchTheCVECVE-2021-27954: A heap-based buffer overflow vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HKProcessConfig
CVE-2021-27954 is a high-severity flaw (CVSS 8.2) affecting ecobee3 lite firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
A heap-based buffer overflow vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HKProcessConfig function of the HomeKit Wireless Access Control setup process. A threat actor can exploit this vulnerability to force the device to connect to a SSID or cause a denial of service.
Why this priority
- High severity
- Public exploit reference
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 8.2 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.9% (top 39%) |
| CISA exploited list | No |
| Weakness | CWE-787 |
| Published | 2021-08-03 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-27954?
ecobee3 lite firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-27954 being exploited?
CVE-2021-27954 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-27954 affect?
CVE-2021-27954 affects ecobee3 lite firmware. Severity is high (CVSS 8.2). A heap-based buffer overflow vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HKProcessConfig function of the HomeKit Wireless Access Control setup process. A threat actor can exploit this vulnerability to force the device
How urgent is CVE-2021-27954?
Priority 54/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2021-27953 HIGH 7.5 MITIGATE A NULL pointer dereference vulnerability exists on the ecobee3 lite 4.5.81.200 device in the HomeKit Wireless
- CVE-2021-27952 CRITICAL 9.8 MITIGATE Hardcoded default root credentials exist on the ecobee3 lite 4.5.81.200 device