CVE-2021-27420Network attack vector

Web-service interruption via unsupported HTTP verbs

Published Mar 23, 2022 · Updated Apr 16, 2025

Improper input validation in GE Multilin Universal Relay firmware before 8.1x allows remote attackers to interrupt its web service. The web-server task mishandles a series of HTTP requests containing unsupported verbs instead of rejecting them while remaining responsive. Unauthenticated network access is sufficient; only the web server becomes temporarily inaccessible, while relay protection and other communications remain operational.

CVSS severity5.3
Medium
EPSS probability1.06%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in GE Multilin Universal Relay firmware before 8.1x allows remote attackers to interrupt its web service. The web-server task mishandles a series of HTTP requests containing unsupported verbs instead of rejecting them while remaining responsive. Unauthenticated network access is sufficient; only the web server becomes temporarily inaccessible, while relay protection and other communications remain operational.

The record

CVE
CVE-2021-27420
Published
Mar 23, 2022
Updated
Apr 16, 2025
Vendor
General Electric
Product
Multilin Universal Relay Family
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <8.1x

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

General Electric · Multilin Universal Relay Familyversion=unspecified <8.1x

Published CVSS scores

5.3ICS-CERTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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-20Improper Input Validation
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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