Client denial of service via pre-authentication EAPOL forwarding
Published May 11, 2021 · Updated Apr 14, 2026
Improper authentication in Siemens SCALANCE W devices allows physically proximate attackers to interrupt connected clients via EAPOL frames. The access-point forwarding path relays EAPOL frames to other clients before the sender has successfully authenticated. Exploitation requires Wi-Fi-range access and can cause client denial of service or facilitate exploitation of separate client flaws.
Summary
What happened
Improper authentication in Siemens SCALANCE W devices allows physically proximate attackers to interrupt connected clients via EAPOL frames. The access-point forwarding path relays EAPOL frames to other clients before the sender has successfully authenticated. Exploitation requires Wi-Fi-range access and can cause client denial of service or facilitate exploitation of separate client flaws.
The record
- CVE
- CVE-2020-26139
- Published
- May 11, 2021
- Updated
- Apr 14, 2026
- Vendor
- Siemens
- Product
- SCALANCE W786-2 RJ45
- Classifications
- CWE-287, T1498
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 11, 2021CVE publishedPublication date reported by the CVE source.
- Apr 14, 2026Record 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.
- Affected versionversion=0 <V6.6.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
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