CVE-2021-22909Network attack vector

Root code execution via disabled certificate validation

Published May 27, 2021 · Updated Aug 3, 2024

Improper certificate validation in Ubiquiti EdgeRouter 2.0.9 and earlier allows remote attackers to execute code as root during updates. The /usr/bin/ubnt-upgrade firmware downloader invokes curl with -k, disabling HTTPS server-certificate verification and accepting attacker-controlled firmware. Exploitation requires a man-in-the-middle position and an administrator-triggered firmware update, after which substituted firmware executes with root privileges.

CVSS severity7.5
High
EPSS probability1.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper certificate validation in Ubiquiti EdgeRouter 2.0.9 and earlier allows remote attackers to execute code as root during updates. The /usr/bin/ubnt-upgrade firmware downloader invokes curl with -k, disabling HTTPS server-certificate verification and accepting attacker-controlled firmware. Exploitation requires a man-in-the-middle position and an administrator-triggered firmware update, after which substituted firmware executes with root privileges.

The record

CVE
CVE-2021-22909
Published
May 27, 2021
Updated
Aug 3, 2024
Vendor
Ubiquiti
Product
EdgeRouter
Classifications
CWE-300, CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 27, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed Version: 2.0.9-hotfix.1 or later.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Ubiquiti · EdgeRouterversion=Fixed Version: 2.0.9-hotfix.1 or later.

Published CVSS scores

7.6National Vulnerability DatabaseAV:N/AC:H/Au:N/C:C/I:C/A:C
7.5National Vulnerability DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
7.5UbiquitiCVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-300Channel Accessible by Non-Endpoint
CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo