MCP-DecayBench Reveals Non-Overlapping Blind Spots in MCP Security Scanners
Resident_Exercise_22 · reddit · 2026-08-13
As MCP (Model Context Protocol) security scanners gain adoption, a developer built MCP-DecayBench, a benchmark to quantify their false-positive rates and detection blind spots.
The core of the benchmark consists of "hard negatives": benign MCP servers built to look malicious (e.g., a legitimate credential helper that reads SSH configs). Testing two major scanners revealed:
- Both catch 100% of actual attacks.
- Both land at a tuned false-positive rate of 0.25.
- Key finding: Their false positives occur on different samples. Cisco's YARA flags defensive tools naming sensitive paths, while Snyk flags backup tools using specific phrasing.
The author notes that a single score is misleading, as blind spots don't overlap. Relying on just one scanner leaves critical security gaps. The project is open-source.
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