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calibremcp MCP Server Security Report

sandraschi/calibremcp

Calibre library automation via FastMCP — metadata, shelves, RAG-friendly export. Companion to Calibre, not a replacement. For Cursor / Claude Desktop.

Security Trust Score
Grade B · Moderate posture
Tier 1 · Public sourceHigh confidence · 98%latest vmaster@47e69e8 Repository
Declared MCP capabilities

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Host sandraschi/calibremcp in a governed environment — SSO in front, every tool call attributed and audited.

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The short answer

Is calibremcp safe to use?
calibremcp scores 88/100 (grade B) on the Canopii Trust Index — good, minor gaps. It passes 15 of the 21 security controls that apply to it, with no confirmed security failures.
How reliable is the security score for calibremcp?
We could evaluate 98% of the controls that apply to calibremcp. Scores are deterministic — the same source always produces the same score — and a partially-scannable server cannot present a high one, because confidence caps the result. The scanner is open source, so this score can be reproduced independently.
How was calibremcp scored?
Its published source was scanned against a fixed catalog of weighted security controls covering code safety, committed secrets, dependency vulnerabilities, tool-description integrity, authentication and transport, and maintenance. A confirmed flaw caps the score outright regardless of what else passes. The full rubric is published.
Reputation50stars11forks2open issues8d agolast commit1yage

Security controlslatest scored version vmaster@47e69e8

Each control is evaluated deterministically with evidence. The score is earned from passing controls; a failed guard caps it.

Model–MCP Runtime Guardrails

  • Warn
    Strict JSON Schema Enforcementschemas not strict

    Tool inputs are constrained (additionalProperties:false), so unexpected arguments can't be smuggled in.

    Fix: Set additionalProperties:false and require explicit parameters on every tool.

  • Pass
    Indirect Prompt Injection (IPI) Defensesguardno injection markers

    Tool/prompt/resource text is free of hidden instructions that could hijack the agent.

  • Pass
    Tool Definition Integrityguardtool definitions stable; no risky changes in version history

    Every consecutive version pair is diffed for new injection markers or destructive scope — a risky diff anywhere in history is a rug-pull (fail, durable); benign description drift warns.

  • Pass
    User-in-the-Loop / Approval Scopeguardno destructive tool scope

    No over-broad or destructive tools (arbitrary shell, bulk-delete) that warrant human approval.

Application Security Checks

  • Warn
    No SSRF sinksguard20 occurrences

    Fetching tool-supplied URLs can pivot into internal networks and metadata services.

    calibre-plugins/calibreops-bridge/client/calibreops_client.py:48calibre-plugins/calibreops-bridge/client/calibreops_client.py:62calibre_plugin/mcp_client.py:24calibre_plugin/mcp_client.py:38

    Fix: Allow-list destinations; reject arbitrary/loopback/link-local URLs.

  • Warn
    No known-vulnerable dependencies11 of 489 runtime deps vulnerable; worst medium

    Runtime dependencies (parsed from the lockfile) are scanned against OSV.dev for published CVEs. Advisory: flagged dependencies lower the score but don't hard-cap it, since transitive reachability is unproven.

    [email protected] — RUSTSEC-2026-0190[email protected] — RUSTSEC-2026-0190[email protected] — GHSA-wrw7-89jp-8q8g[email protected] — RUSTSEC-2024-0429

    Fix: Upgrade the flagged dependencies past their fixed versions.

  • Pass
    No command-injection sinksguardno sinks found

    Untrusted tool input reaching a shell yields remote code execution.

  • Pass
    No dynamic code executionguardno sinks found

    eval()/exec()/Function() on tool-derived strings allows arbitrary code execution.

  • Pass
    No path traversalguardno sinks found

    Naive path checks let tools read/write outside intended directories (EscapeRoute-class).

  • Pass
    No unsafe deserializationguardno sinks found

    pickle/yaml.load/etc. on untrusted data can execute code.

  • Pass
    No committed secretsguardno secrets found

    Hardcoded keys/tokens in published source are live credentials an attacker can use.

  • Pass
    Credentials sourced from environmentreads credentials from environment

    Reading secrets from env/secret stores avoids hardcoding them.

  • Pass
    Dependencies pinned (lockfile)lockfile present

    A lockfile makes installs reproducible and resistant to silent dependency swaps.

  • Pass
    Actively maintainedrecent commits

    Unmaintained servers don't receive security fixes.

  • Pass
    Repository not archivedguardactive

    Archived repositories will never be patched.

  • Pass
    Declares a licenseMIT

    A clear license is required for legal enterprise use.

  • Pass
    Has a security policySECURITY.md present

    A SECURITY.md gives a private path to report vulnerabilities.

  • Pass
    Adoption & popularityestablished adoption

    A small, capped nudge from stars/downloads — widely-used servers get more eyes on bugs. It can never offset a real security failure.

  • Not checked
    Signed releasesnot evaluated

    Signed releases let consumers verify artifacts weren't tampered with.

  • N/A
    No install/post-install scriptsguardno published package

    install hooks run arbitrary code on every consumer at install time.

  • N/A
    Package name not typosquattingguardno published package

    Names mimicking popular packages are a common malware delivery vector.

  • N/A
    Published with provenanceno published package

    Build provenance attests the artifact was built from the claimed source by CI.

  • N/A
    Established maintainerno published package

    Brand-new / single anonymous maintainers raise takeover and malware risk.

Transport & Trust Model

  • Warn
    Execution Sandboxingruns natively (no container image)

    A container/sandbox image limits blast radius; a server that runs natively has full host access.

    Fix: Ship a Dockerfile/Containerfile (or document a sandboxed run) so the server runs isolated.

  • Warn
    Network Exposurebinds 0.0.0.0

    Binding 0.0.0.0 or exposing debug inspectors widens the attack surface.

    Fix: Bind to 127.0.0.1 by default; never ship open debug endpoints.

  • N/A
    Transport Encryption (TLS)guardno remote endpoints

    Plaintext HTTP exposes traffic and bearer tokens to interception.

  • N/A
    IAM / Authentication Scopingno remote endpoints

    OAuth 2.1 / Protected Resource Metadata gates who can invoke tools.

  • N/A
    Live Endpoint Reachablenot dynamically scanned

    A dynamic scan connected to the declared remote endpoint and it responded — verified live, not a dead URL.

  • N/A
    Authentication Enforced (live)not dynamically scanned

    If the server declares auth is required, it must actually reject anonymous clients. Serving tools to unauthenticated callers is a real exposure.

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Versions

VersionScoreStatus
vmaster@47e69e8latest88Bscored
vmaster@5abaad688Bscored
vmaster@ce9be2a88Bscored
vmaster@5a5c8bb88Bscored
vmaster@b389dee88Bscored
vmaster@2c7d22c88Bscored
vmaster@0432adb88Bscored
vmaster@6c86c1a88Bscored
vmaster@7fa5b8988Bscored
vmaster@f80cf2588Bscored
vmaster@486574688Bscored
vmaster@43a59bc88Bscored
vmaster@9bed52488Bscored
vmaster@5f99bda88Bscored
vmaster@06cf45e88Bscored
vmaster@774d7bc15Fscored
vmaster@7218fa615Fscored
vmaster@55e45f815Fscored
vmaster@1125c3f15Fscored
vmaster@6a7dc6215Fscored

Wondering how this compares? The MCP Security Index tracks grade distribution, committed secrets, and missing authentication across the whole ecosystem, refreshed monthly.