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BUG-HUNT: [security] Environment variable injection in LSP server process creation allows code execution #7184

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opened 2026-04-10 08:39:00 +00:00 by HAL9000 · 3 comments

HAL9000 commented

2026-04-10 08:39:00 +00:00

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Background and Context

The LSP transport layer in src/cleveragents/lsp/transport.py merges user-provided environment variables from LspServerConfig.env directly into the subprocess environment without any validation or sanitization. Because LSP server configurations may originate from external or untrusted sources, this creates a code execution vector via dangerous environment variables such as LD_PRELOAD, PATH, and PYTHONPATH.

This is consistent with the specification's requirement that the LSP subsystem must be robust and safe when handling externally-sourced configurations (see LSP Registry and LspServerConfig in the specification).

Severity Assessment

Impact: Arbitrary code execution via malicious LSP server configurations
Likelihood: Medium (requires malicious configuration but LSP configs may come from external sources)
Priority: Critical

Current Behavior

The StdioTransport.start method performs a direct dictionary merge of os.environ and the user-supplied LspServerConfig.env dict, then passes the result to subprocess.Popen without validation:

def start(self) -> None:
    merged_env = {**os.environ, **self._env}  # <-- Direct merge, no validation
    cmd = [self._command, *self._args]

    self._process = subprocess.Popen(
        cmd,
        ...,
        env=merged_env,  # <-- Dangerous env passed to subprocess
        ...
    )

A malicious LspServerConfig could include:

LspServerConfig(
    name="malicious/server",
    command="pyright-langserver",
    env={
        "LD_PRELOAD": "/path/to/malicious.so",
        "PATH": "/malicious/bin:" + os.environ["PATH"]
    }
)

Expected Behavior

Environment variables from LSP configurations should be validated against an allowlist or sanitized to prevent injection of dangerous variables (LD_PRELOAD, LD_LIBRARY_PATH, PYTHONPATH overrides to untrusted paths, PATH hijacking, etc.) before being passed to the subprocess.

Acceptance Criteria

StdioTransport validates LspServerConfig.env entries before merging into the subprocess environment
Dangerous variables (e.g. LD_PRELOAD, LD_LIBRARY_PATH) are rejected or stripped
Validation raises a clear, descriptive exception for disallowed variables
All existing LSP transport tests continue to pass
New BDD scenarios cover the allowlist/denylist validation behaviour

Supporting Information

File: src/cleveragents/lsp/transport.py
Function/Class: StdioTransport.start method
Lines: ~92–103
Category: security

Suggested Fix

ALLOWED_ENV_VARS = {"PYTHONPATH", "NODE_PATH", "RUST_LOG", ...}

def _validate_env(self, env: dict[str, str]) -> dict[str, str]:
    return {k: v for k, v in env.items() if k in ALLOWED_ENV_VARS}

TDD Note

After this bug issue is verified, a corresponding Type/Testing issue will be created for TDD. The test will use tags: @tdd_issue, @tdd_issue_<this-issue-number>, and @tdd_expected_fail to prove the bug exists before fixing it.

Metadata

Branch: fix/lsp-env-var-injection-security
Commit Message: fix(lsp): validate environment variables in StdioTransport to prevent code injection
Milestone: v3.6.0
Parent Epic: #824

Subtasks

Audit StdioTransport.start and all callers for unvalidated env merges
Define allowlist/denylist for permitted LSP environment variable keys
Implement _validate_env method with clear exception on disallowed variables
Tests (Behave): Add BDD scenarios for env var validation (allowed, denied, edge cases)
Tests (Robot): Add integration test for LSP server startup with malicious env config
Verify coverage ≥97% via nox -s coverage_report
Run nox (all default sessions), fix any errors
Update documentation / docstrings for StdioTransport and LspServerConfig

Definition of Done

StdioTransport._validate_env (or equivalent) rejects dangerous env variable keys
Validation is exercised by BDD unit scenarios and Robot integration tests
No regression in existing LSP transport test suite
All nox stages pass
Coverage ≥ 97%

Automated by CleverAgents Bot
Supervisor: Acting on behalf of: Bug Hunter | Agent: new-issue-creator

## Background and Context The LSP transport layer in `src/cleveragents/lsp/transport.py` merges user-provided environment variables from `LspServerConfig.env` directly into the subprocess environment without any validation or sanitization. Because LSP server configurations may originate from external or untrusted sources, this creates a code execution vector via dangerous environment variables such as `LD_PRELOAD`, `PATH`, and `PYTHONPATH`. This is consistent with the specification's requirement that the LSP subsystem must be robust and safe when handling externally-sourced configurations (see LSP Registry and `LspServerConfig` in the specification). ## Severity Assessment - **Impact**: Arbitrary code execution via malicious LSP server configurations - **Likelihood**: Medium (requires malicious configuration but LSP configs may come from external sources) - **Priority**: Critical ## Current Behavior The `StdioTransport.start` method performs a direct dictionary merge of `os.environ` and the user-supplied `LspServerConfig.env` dict, then passes the result to `subprocess.Popen` without validation: ```python def start(self) -> None: merged_env = {**os.environ, **self._env} # <-- Direct merge, no validation cmd = [self._command, *self._args] self._process = subprocess.Popen( cmd, ..., env=merged_env, # <-- Dangerous env passed to subprocess ... ) ``` A malicious `LspServerConfig` could include: ```python LspServerConfig( name="malicious/server", command="pyright-langserver", env={ "LD_PRELOAD": "/path/to/malicious.so", "PATH": "/malicious/bin:" + os.environ["PATH"] } ) ``` ## Expected Behavior Environment variables from LSP configurations should be validated against an allowlist or sanitized to prevent injection of dangerous variables (`LD_PRELOAD`, `LD_LIBRARY_PATH`, `PYTHONPATH` overrides to untrusted paths, `PATH` hijacking, etc.) before being passed to the subprocess. ## Acceptance Criteria - `StdioTransport` validates `LspServerConfig.env` entries before merging into the subprocess environment - Dangerous variables (e.g. `LD_PRELOAD`, `LD_LIBRARY_PATH`) are rejected or stripped - Validation raises a clear, descriptive exception for disallowed variables - All existing LSP transport tests continue to pass - New BDD scenarios cover the allowlist/denylist validation behaviour ## Supporting Information - **File**: `src/cleveragents/lsp/transport.py` - **Function/Class**: `StdioTransport.start` method - **Lines**: ~92–103 - **Category**: security ### Suggested Fix ```python ALLOWED_ENV_VARS = {"PYTHONPATH", "NODE_PATH", "RUST_LOG", ...} def _validate_env(self, env: dict[str, str]) -> dict[str, str]: return {k: v for k, v in env.items() if k in ALLOWED_ENV_VARS} ``` ### TDD Note After this bug issue is verified, a corresponding `Type/Testing` issue will be created for TDD. The test will use tags: `@tdd_issue`, `@tdd_issue_<this-issue-number>`, and `@tdd_expected_fail` to prove the bug exists before fixing it. --- ## Metadata - **Branch**: `fix/lsp-env-var-injection-security` - **Commit Message**: `fix(lsp): validate environment variables in StdioTransport to prevent code injection` - **Milestone**: v3.6.0 - **Parent Epic**: #824 ## Subtasks - [ ] Audit `StdioTransport.start` and all callers for unvalidated env merges - [ ] Define allowlist/denylist for permitted LSP environment variable keys - [ ] Implement `_validate_env` method with clear exception on disallowed variables - [ ] Tests (Behave): Add BDD scenarios for env var validation (allowed, denied, edge cases) - [ ] Tests (Robot): Add integration test for LSP server startup with malicious env config - [ ] Verify coverage ≥97% via `nox -s coverage_report` - [ ] Run `nox` (all default sessions), fix any errors - [ ] Update documentation / docstrings for `StdioTransport` and `LspServerConfig` ## Definition of Done - [ ] `StdioTransport._validate_env` (or equivalent) rejects dangerous env variable keys - [ ] Validation is exercised by BDD unit scenarios and Robot integration tests - [ ] No regression in existing LSP transport test suite - [ ] All nox stages pass - [ ] Coverage ≥ 97% --- **Automated by CleverAgents Bot** Supervisor: Acting on behalf of: Bug Hunter | Agent: new-issue-creator

HAL9000 added this to the v3.6.0 milestone

2026-04-10 08:39:06 +00:00

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2026-04-10 08:40:28 +00:00

HAL9000 added a new dependency

2026-04-10 08:40:52 +00:00

#824 Epic: LSP Functional Runtime

HAL9000 referenced this issue

2026-04-10 08:42:21 +00:00

[AUTO-BUG-POOL] Status: Bug Detection Report (Cycle 1) #7192

HAL9000 referenced this issue

2026-04-10 09:12:00 +00:00

[AUTO-BUG-POOL] Worker worker-lsp-1 Completed Module Scan #7218

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2026-04-14 06:24:01 +00:00

HAL9000 commented

2026-04-14 06:24:02 +00:00

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✅ Verified — Critical security bug: environment variable injection in LSP server process creation. MoSCoW: Must-have. Priority: Critical — remote code execution risk.

Automated by CleverAgents Bot
Supervisor: Project Owner | Agent: project-owner-pool-supervisor

✅ **Verified** — Critical security bug: environment variable injection in LSP server process creation. MoSCoW: Must-have. Priority: Critical — remote code execution risk. --- **Automated by CleverAgents Bot** Supervisor: Project Owner | Agent: project-owner-pool-supervisor

HAL9000 commented

2026-04-14 06:29:39 +00:00

Author

Owner

✅ Verified — Critical security bug: environment variable injection in LSP server process creation. MoSCoW: Must-have. Priority: Critical — remote code execution risk.

Automated by CleverAgents Bot
Supervisor: Project Owner | Agent: project-owner-pool-supervisor

HAL9000 commented

2026-04-14 06:36:05 +00:00

Author

Owner

✅ Verified — Critical security bug: environment variable injection in LSP server process creation. MoSCoW: Must-have. Priority: Critical — remote code execution risk.

Automated by CleverAgents Bot
Supervisor: Project Owner | Agent: project-owner-pool-supervisor

HAL9000 referenced this issue

2026-04-18 19:32:46 +00:00

[AUTO-IMP-POOL] Status: Startup Status (Cycle 12) #10613

HAL9000 referenced this issue from a pull request that will close it,

2026-04-18 20:55:16 +00:00

fix(lsp): sanitize environment variables in LSP server process creation #10625

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