Authenticated denial of service via undersized portList buffer
Published Aug 24, 2026 · Updated Aug 24, 2026
Buffer overflow in DrayTek VigorSwitch mainfunction.cgi firmware allows remote authenticated users to interrupt service via crafted input. The switch_lan_gvrp function copies the portList field into a destination buffer that is too small, overwriting adjacent memory. Administrative web-interface credentials are required; DrayTek reports no documented trigger, practical attack path, or demonstrated command execution.
Summary
What happened
Buffer overflow in DrayTek VigorSwitch mainfunction.cgi firmware allows remote authenticated users to interrupt service via crafted input. The switch_lan_gvrp function copies the portList field into a destination buffer that is too small, overwriting adjacent memory. Administrative web-interface credentials are required; DrayTek reports no documented trigger, practical attack path, or demonstrated command execution.
The record
- CVE
- CVE-2026-71938
- Published
- Aug 24, 2026
- Updated
- Aug 24, 2026
- Vendor
- DrayTek
- Product
- VigorSwitch P2100
- Classifications
- CWE-120
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Aug 24, 2026CVE publishedPublication date reported by the CVE source.
- Aug 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <2.9.10
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
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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