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CVE-2021-33539: In Weidmueller Industrial WLAN devices in multiple versions an exploitable authentication bypass vulnerability

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HIGH 7.2UPGRADEUPGRADEUPGRADE

CVE-2021-33539 is a high-severity flaw (CVSS 7.2) affecting ie-wl-bl-ap-cl-eu firmware, ie-wlt-bl-ap-cl-eu firmware, ie-wl-bl-ap-cl-us firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Weidmueller Industrial WLAN devices in multiple versions an exploitable authentication bypass vulnerability exists in the hostname processing. A specially configured device hostname can cause the device to interpret selected remote traffic as local traffic, resulting in a bypass of web authentication. An attacker can send authenticated SNMP requests to trigger this vulnerability.

Why this priority

  • High severity

A fixed release or distro patch exists.

Risk facts

CVSS score7.2 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededHigh
User interactionNone
EPSS exploit chance1.1% (top 36%)
CISA exploited listNo
WeaknessCWE-287
Published2021-06-25
Last modified2026-06-17
Publisher (CNA): CERT VDE · Vendor: weidmueller

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

weidmueller ie-wl-bl-ap-cl-eu firmware UPGRADE
Affected: <= 1.16.18 · <= 1.11.10
Fixed in: newer than 1.16.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
weidmueller ie-wlt-bl-ap-cl-eu firmware UPGRADE
Affected: <= 1.16.18 · <= v1.11.10
Fixed in: newer than v1.11.10
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
weidmueller ie-wl-bl-ap-cl-us firmware UPGRADE
Affected: <= 1.16.18 · <= 1.11.10
Fixed in: newer than 1.16.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
weidmueller ie-wlt-bl-ap-cl-us firmware UPGRADE
Affected: <= 1.16.18 · <= 1.11.10
Fixed in: newer than 1.16.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
weidmueller ie-wl-vl-ap-br-cl-eu firmware UPGRADE
Affected: <= 1.16.18 · <= 1.11.10
Fixed in: newer than 1.16.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
weidmueller ie-wlt-vl-ap-br-cl-eu firmware UPGRADE
Affected: <= 1.16.18 · <= 1.11.10
Fixed in: newer than 1.16.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
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-2021-33539?

ie-wl-bl-ap-cl-eu firmware: upgrade to newer than 1.16.18; ie-wlt-bl-ap-cl-eu firmware: upgrade to newer than v1.11.10; ie-wl-bl-ap-cl-us firmware: upgrade to newer than 1.16.18. Exact commands for each OS are on this page.

Is CVE-2021-33539 being exploited?

CVE-2021-33539 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-2021-33539 affect?

CVE-2021-33539 affects ie-wl-bl-ap-cl-eu firmware, ie-wlt-bl-ap-cl-eu firmware, ie-wl-bl-ap-cl-us firmware. Severity is high (CVSS 7.2). In Weidmueller Industrial WLAN devices in multiple versions an exploitable authentication bypass vulnerability exists in the hostname processing. A specially configured device hostname can cause the device to interpret selected remote traff

How urgent is CVE-2021-33539?

Priority 41/100. High severity

Related CVEs

References

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