server-filesystem
npm:@modelcontextprotocol/server-filesystem@2026.1.14
github.com/modelcontextprotocol/servers
Severity breakdown
Worst finding
Tool `write_file` name implies a side effect that is not declared
· write_file
`write_file` looks like a side-effecting tool (its name contains a mutation verb), but its `side_effects` declaration is []. A policy synthesizer cannot produce safe rules for this tool because it cannot tell what it actually does.
fix: Declare the tool's true side effects explicitly. If the tool is genuinely read-only, rename it to match (e.g. `email.preview` rather than `email.send`).
All 15 findings
- highTool `write_file` name implies a side effect that is not declared· write_fileexcessive agency
`write_file` looks like a side-effecting tool (its name contains a mutation verb), but its `side_effects` declaration is []. A policy synthesizer cannot produce safe rules for this tool because it cannot tell what it actually does.
fix: Declare the tool's true side effects explicitly. If the tool is genuinely read-only, rename it to match (e.g. `email.preview` rather than `email.send`).
- highTool `edit_file` name implies a side effect that is not declared· edit_fileexcessive agency
`edit_file` looks like a side-effecting tool (its name contains a mutation verb), but its `side_effects` declaration is []. A policy synthesizer cannot produce safe rules for this tool because it cannot tell what it actually does.
fix: Declare the tool's true side effects explicitly. If the tool is genuinely read-only, rename it to match (e.g. `email.preview` rather than `email.send`).
- highTool `create_directory` name implies a side effect that is not declared· create_directoryexcessive agency
`create_directory` looks like a side-effecting tool (its name contains a mutation verb), but its `side_effects` declaration is []. A policy synthesizer cannot produce safe rules for this tool because it cannot tell what it actually does.
fix: Declare the tool's true side effects explicitly. If the tool is genuinely read-only, rename it to match (e.g. `email.preview` rather than `email.send`).
- mediumTool `read_file` accepts unconstrained string input· read_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `read_text_file` accepts unconstrained string input· read_text_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `read_media_file` accepts unconstrained string input· read_media_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `write_file` accepts unconstrained string input· write_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `content`, `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `edit_file` accepts unconstrained string input· edit_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `create_directory` accepts unconstrained string input· create_directoryunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `list_directory` accepts unconstrained string input· list_directoryunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `list_directory_with_sizes` accepts unconstrained string input· list_directory_with_sizesunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`, `sortBy`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `directory_tree` accepts unconstrained string input· directory_treeunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `move_file` accepts unconstrained string input· move_fileunconstrained input
The following string parameter(s) have no `maxLength` constraint: `destination`, `source`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `search_files` accepts unconstrained string input· search_filesunconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`, `pattern`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
- mediumTool `get_file_info` accepts unconstrained string input· get_file_infounconstrained input
The following string parameter(s) have no `maxLength` constraint: `path`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.
fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.
How this was scored
Source sandbox — live tools/list captured in an ephemeral Docker container (parameter schemas included → R1/R2/R4 fire). Findings are emitted by the public capframe.findings.v1 schema. Score = 100 − (10·Critical + 4·High + 2·Medium + 1·Low), clamped to [0, 100].
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