CVE-2021-33539Network attack vector

Authenticated web bypass via hostname traffic confusion

Published Jun 25, 2021 · Updated Sep 16, 2024

Authentication bypass in Weidmüller IE-WL(T)-BL-AP-CL and IE-WL(T)-VL-AP-BR-CL devices through firmware V1.16.18 and V1.11.10 allows remote authenticated users to bypass web authentication via SNMP-triggered hostname processing. The hostname-processing path treats selected remote traffic as local traffic when a specially configured device hostname is present, causing the web interface to skip authentication checks. Access requires authenticated SNMP requests and the crafted hostname condition; successful exploitation bypasses web login and can expose or alter management functions.

CVSS severity7.2
High
EPSS probability1.06%
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

Authentication bypass in Weidmüller IE-WL(T)-BL-AP-CL and IE-WL(T)-VL-AP-BR-CL devices through firmware V1.16.18 and V1.11.10 allows remote authenticated users to bypass web authentication via SNMP-triggered hostname processing. The hostname-processing path treats selected remote traffic as local traffic when a specially configured device hostname is present, causing the web interface to skip authentication checks. Access requires authenticated SNMP requests and the crafted hostname condition; successful exploitation bypasses web login and can expose or alter management functions.

The record

CVE
CVE-2021-33539
Published
Jun 25, 2021
Updated
Sep 16, 2024
Vendor
Weidmüller
Product
IE-WL(T)-BL-AP-CL
Classifications
CWE-287, T1021
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=IE-WL-BL-AP-CL-EU (2536600000) <=V1.16.18 (Build 18081617)
  2. Affected versionversion=IE-WL-BL-AP-CL-US (2536660000) <=V1.16.18 (Build 18081617)
  3. Affected versionversion=IE-WLT-BL-AP-CL-EU (2536650000) <=V1.16.18 (Build 18081617)
  4. Affected versionversion=IE-WLT-BL-AP-CL-US (2536670000) <=V1.16.18 (Build 18081617)

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Weidmüller · IE-WL(T)-BL-AP-CLversion=IE-WL-BL-AP-CL-EU (2536600000) <=V1.16.18 (Build 18081617); version=IE-WL-BL-AP-CL-US (2536660000) <=V1.16.18 (Build 18081617); version=IE-WLT-BL-AP-CL-EU (2536650000) <=V1.16.18 (Build 18081617); version=IE-WLT-BL-AP-CL-US (2536670000) <=V1.16.18 (Build 18081617)
Weidmüller · IE-WL(T)-VL-AP-BR-CLversion=IE-WLT-VL-AP-BR-CL-EU (2536690000) <=V1.11.10 (Build 18122616); version=IE-WLT-VL-AP-BR-CL-US (2536710000) <=V1.11.10 (Build 18122616); version=IE-WL-VL-AP-BR-CL-EU (2536680000) <=V1.11.10 (Build 18122616); version=IE-WL-VL-AP-BR-CL-US (2536700000) <=V1.11.10 (Build 18122616)

Published CVSS scores

7.2CERT@VDECVSS:3.1/AV:N/AC:L/PR:H/UI:N/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1021External Remote Services

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