CVE-2021-27954Public exploitNetwork attack vector

Wi-Fi reassociation or denial-of-service via heap overflow

Published Aug 3, 2021 · Updated Aug 3, 2024

Heap-based buffer overflow in ecobee3 lite 4.5.81.200 allows remote attackers to force Wi-Fi reassociation or interrupt service. HKProcessConfig accepts an unauthenticated POST body at TCP port 1200 /config and lets data beyond 604 bytes corrupt the next heap object. The WAC service remains reachable after initial setup; shorter oversized bodies can change control flags and the SSID, while larger bodies corrupt adjacent heap memory.

CVSS severity8.2
High
EPSS probability0.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in ecobee3 lite 4.5.81.200 allows remote attackers to force Wi-Fi reassociation or interrupt service. HKProcessConfig accepts an unauthenticated POST body at TCP port 1200 /config and lets data beyond 604 bytes corrupt the next heap object. The WAC service remains reachable after initial setup; shorter oversized bodies can change control flags and the SSID, while larger bodies corrupt adjacent heap memory.

The record

CVE
CVE-2021-27954
Published
Aug 3, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.4NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:P
8.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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