CVE-2021-34561
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn PEPPERL+FUCHS WirelessHART-Gateway <= 3.0.8 serious issue exists, if the application is not externally accessible or uses IP-based access restrictions. Attackers can use DNS Rebinding to bypass any IP or firewall based access restrictions that may be in place, by proxying through their target's browser.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThe PEPPERL+FUCHS WirelessHART-Gateway <= 3.0.8 is vulnerable to DNS rebinding attacks that bypass IP-based access controls. Attackers exploit the browser's Same-Origin Policy by controlling DNS responses to first resolve to an allowed external IP, then to an internal IP after the TTL expires, effectively proxying malicious requests through the victim's browser to reach internal network resources.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 3.0.8<= 3.0.8CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Pepperl Fuchs WirelessHART Gateway on the networkScan network for devices with WirelessHART Gateway fingerprints (check HTTP headers, SNMP OIDs, or device discovery). Look for device responses containing 'Pepperl+Fuchs' or 'WirelessHART' in banners or DHCP fingerprints.Affected if The device is present on the network and is a Pepperl Fuchs WirelessHART Gateway with HTTP/HTTPS interface accessible.
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Check the firmware versionAccess the device web interface or use SNMP to query the firmware version. Common SNMP OID: .1.3.6.1.4.1.12356.1.1 (or check via HTTP /about page if available). Compare the version number to 3.0.8.Affected if Firmware version is 3.0.8 or lower.
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Verify IP-based access control configurationLog into the device administrative interface and navigate to Network Settings or Access Control. Check if IP allowlisting or IP-based authentication is configured as a primary security mechanism.Affected if IP-based access controls (allowlisting or source IP restrictions) are configured as the sole or primary authentication method.
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Check DNS rebinding protectionsExamine the device or upstream network equipment for DNS rebinding mitigations: DNS pinning, host header validation, or DNS filtering that rejects unexpected TTL values or unauthorized domain resolution.Affected if No DNS rebinding protections are configured and the device relies on DNS for name resolution.
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Test DNS rebinding susceptibilityFrom an external system, attempt a DNS rebinding attack simulation: register a domain with very short TTL (e.g., 1-30 seconds), configure it to first resolve to an IP on the device's allowed list, then change to an internal IP address after TTL expiry. Observe if the device accepts the rebinding request.Affected if The device accepts requests from IPs that change via DNS rebinding, indicating the vulnerability is exploitable.
The environment is affected if a Pepperl Fuchs WirelessHART Gateway with firmware <= 3.0.8 is using IP-based access controls without DNS rebinding protections, allowing an attacker to bypass those controls via DNS rebinding.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedImplement defense-in-depth by adding proper authentication mechanisms (e.g., API keys, tokens) rather than relying solely on IP allowlisting; configure DNS rebinding protections such as DNS pinning, host header validation, or network-level DNS filtering.
Any firmware version above 3.0.8 (refer to cert.vde.com for the exact fixed release number)
- 1. Identify the current firmware version of the PEPPERL+FUCHS WirelessHART-Gateway device
- 2. Download the latest firmware version from the official PEPPERL+FUCHS support portal or reference cert.vde.com for the fixed release
- 3. Backup the current device configuration before performing the firmware upgrade
- 4. Follow the manufacturer's official firmware upgrade procedure to install the fixed version (version > 3.0.8)
- 5. After upgrading, verify that the DNS rebinding protection is properly functioning and access restrictions are enforced
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34561 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-34561 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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