This release includes 1 security fix for security teams reviewing exposed deployments.
Topics
+3 more
Affected surfaces
Summary
AI summaryFixes a read‑only mode bypass allowing writes via aggregation pipelines
Full changelog
Security fix
Fixes a read-only mode bypass in the aggregate tool. When the server was started with --read-only (or MCP_MONGODB_READONLY=true), an aggregation pipeline containing $out or $merge could still write to or replace collections, bypassing the read-only protection. Server-side JavaScript operators ($function, $accumulator, $where) are now rejected in read-only mode as well.
Affected: all versions up to and including 2.1.0 when run in read-only mode.
Fixed: aggregation pipelines are now recursively checked and these operators are rejected under read-only mode. Normal (writable) mode is unchanged.
For defense in depth, we also recommend enforcing read-only access at the database level with a read-only MongoDB user.
Full Changelog: https://github.com/kiliczsh/mcp-mongo-server/compare/2.1.0...2.1.1
Security Fixes
- Fixes bypass of --read-only/MCP_MONGODB_READONLY where aggregation pipelines with $out, $merge and JS operators ($function,$accumulator,$where) could still write data
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Beta — feedback welcome: [email protected]