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BUG-HUNT: [security] Environment variable injection vulnerability in config parser allows arbitrary content injection #7191

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opened 2026-04-10 08:42:04 +00:00 by HAL9000 · 3 comments

HAL9000 commented

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

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Background

The reactive configuration parser (src/cleveragents/reactive/config_parser.py) performs environment variable interpolation without sanitising the substituted values. The regex pattern r"\${([A-Za-z0-9_]+)(?::([^}]*))?}" allows any content in the default value part ([^}]*), and both environment variable values and defaults are returned without validation or sanitisation. This creates a security vulnerability where malicious environment variables can inject arbitrary content into configuration processing.

This is a security-critical issue affecting the core reactive configuration subsystem. Any code path that calls ReactiveConfigParser._interpolate_env() is affected.

Severity Assessment

Impact: Malicious environment variables can inject arbitrary content into configuration processing, potentially compromising system integrity
Likelihood: High — environment variables are commonly used and controlled by deployment environments (CI/CD, containers, orchestration platforms)
Priority: Critical

Location

File: src/cleveragents/reactive/config_parser.py
Function: ReactiveConfigParser._interpolate_env()
Lines: 65–72

Current Behavior

The _interpolate_env() method returns raw environment variable values and defaults without any sanitisation:

def repl(match: re.Match[str]) -> str:
    var = match.group(1)
    default = match.group(2)  # This can contain any characters except }
    val = os.environ.get(var, default)
    if val is None:
        raise ConfigurationError(f"Environment variable '{var}' is not set")
    return str(val)  # No sanitization of returned value

The regex r"\${([A-Za-z0-9_]+)(?::([^}]*))?}" allows any content in the default value part ([^}]*), and the environment variable value is returned without validation. This means:

Default values embedded in config files can contain arbitrary content (e.g., ${VAR:malicious_default_content})
Environment variable values are substituted verbatim without any content validation or escaping

Expected Behavior

Environment variable values and defaults should be sanitised and validated before substitution to prevent injection of malicious content into configuration processing. Substituted values should be treated as safe scalars, not raw markup.

Suggested Fix

Validate and sanitise environment variable values before substitution.
Restrict default value content to safe characters (e.g., alphanumeric, basic punctuation) rather than allowing any non-} character.
Consider escaping or quoting substituted values to ensure they are treated as scalars in downstream processing.
Add explicit content validation to reject values containing potentially dangerous patterns.

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: bugfix/m3-env-var-injection-config-parser
Commit Message: fix(config): sanitise and validate env var values in _interpolate_env to prevent injection
Milestone: v3.2.0
Parent Epic: #5502

Subtasks

Reproduce the injection with a targeted BDD scenario tagged @tdd_issue, @tdd_issue_<N>, @tdd_expected_fail
Audit the regex pattern for default value content restrictions and tighten to safe characters only
Implement sanitisation/validation of environment variable values before substitution in ReactiveConfigParser._interpolate_env()
Implement sanitisation/validation of default values in the regex match
Verify fix prevents injection while preserving legitimate environment variable usage
Remove @tdd_expected_fail tag from the TDD scenario once the fix is in place
Update docstring and inline comments to document the security contract
Confirm no regression in existing config-parser BDD scenarios

Definition of Done

A BDD scenario (tagged @tdd_issue and @tdd_issue_<N>) demonstrates the injection vector and passes after the fix
ReactiveConfigParser._interpolate_env() no longer allows arbitrary content injection via environment variable values or defaults
Default value regex pattern is restricted to safe characters only
All existing ReactiveConfigParser BDD scenarios continue to pass
Pyright strict-mode type checking passes with zero errors (nox -s typecheck)
Ruff linting passes with zero violations (nox -s lint)
Security scan passes with no new high/critical findings (nox -s security_scan)
All nox stages pass
Coverage >= 97%

Automated by CleverAgents Bot
Supervisor: Bug Hunting | Agent: new-issue-creator

## Background The reactive configuration parser (`src/cleveragents/reactive/config_parser.py`) performs environment variable interpolation without sanitising the substituted values. The regex pattern `r"\${([A-Za-z0-9_]+)(?::([^}]*))?}"` allows any content in the default value part `([^}]*)`, and both environment variable values and defaults are returned without validation or sanitisation. This creates a security vulnerability where malicious environment variables can inject arbitrary content into configuration processing. This is a security-critical issue affecting the core reactive configuration subsystem. Any code path that calls `ReactiveConfigParser._interpolate_env()` is affected. ## Severity Assessment - **Impact**: Malicious environment variables can inject arbitrary content into configuration processing, potentially compromising system integrity - **Likelihood**: High — environment variables are commonly used and controlled by deployment environments (CI/CD, containers, orchestration platforms) - **Priority**: Critical ## Location - **File**: `src/cleveragents/reactive/config_parser.py` - **Function**: `ReactiveConfigParser._interpolate_env()` - **Lines**: 65–72 ## Current Behavior The `_interpolate_env()` method returns raw environment variable values and defaults without any sanitisation: ```python def repl(match: re.Match[str]) -> str: var = match.group(1) default = match.group(2) # This can contain any characters except } val = os.environ.get(var, default) if val is None: raise ConfigurationError(f"Environment variable '{var}' is not set") return str(val) # No sanitization of returned value ``` The regex `r"\${([A-Za-z0-9_]+)(?::([^}]*))?}"` allows any content in the default value part `([^}]*)`, and the environment variable value is returned without validation. This means: 1. Default values embedded in config files can contain arbitrary content (e.g., `${VAR:malicious_default_content}`) 2. Environment variable values are substituted verbatim without any content validation or escaping ## Expected Behavior Environment variable values and defaults should be sanitised and validated before substitution to prevent injection of malicious content into configuration processing. Substituted values should be treated as safe scalars, not raw markup. ## Suggested Fix 1. Validate and sanitise environment variable values before substitution. 2. Restrict default value content to safe characters (e.g., alphanumeric, basic punctuation) rather than allowing any non-`}` character. 3. Consider escaping or quoting substituted values to ensure they are treated as scalars in downstream processing. 4. Add explicit content validation to reject values containing potentially dangerous patterns. ## 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**: `bugfix/m3-env-var-injection-config-parser` - **Commit Message**: `fix(config): sanitise and validate env var values in _interpolate_env to prevent injection` - **Milestone**: v3.2.0 - **Parent Epic**: #5502 ## Subtasks - [ ] Reproduce the injection with a targeted BDD scenario tagged `@tdd_issue`, `@tdd_issue_<N>`, `@tdd_expected_fail` - [ ] Audit the regex pattern for default value content restrictions and tighten to safe characters only - [ ] Implement sanitisation/validation of environment variable values before substitution in `ReactiveConfigParser._interpolate_env()` - [ ] Implement sanitisation/validation of default values in the regex match - [ ] Verify fix prevents injection while preserving legitimate environment variable usage - [ ] Remove `@tdd_expected_fail` tag from the TDD scenario once the fix is in place - [ ] Update docstring and inline comments to document the security contract - [ ] Confirm no regression in existing config-parser BDD scenarios ## Definition of Done - [ ] A BDD scenario (tagged `@tdd_issue` and `@tdd_issue_<N>`) demonstrates the injection vector and passes after the fix - [ ] `ReactiveConfigParser._interpolate_env()` no longer allows arbitrary content injection via environment variable values or defaults - [ ] Default value regex pattern is restricted to safe characters only - [ ] All existing `ReactiveConfigParser` BDD scenarios continue to pass - [ ] Pyright strict-mode type checking passes with zero errors (`nox -s typecheck`) - [ ] Ruff linting passes with zero violations (`nox -s lint`) - [ ] Security scan passes with no new high/critical findings (`nox -s security_scan`) - [ ] All nox stages pass - [ ] Coverage >= 97% --- **Automated by CleverAgents Bot** Supervisor: Bug Hunting | Agent: new-issue-creator

HAL9000 added this to the v3.2.0 milestone

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

HAL9000 added the

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2026-04-10 08:46:04 +00:00

HAL9000 added a new dependency

2026-04-10 08:47:01 +00:00

#5502 EPIC: Actor Execution & Configuration — GRAPH Actor, Config Schema & CLI Compliance (v3.5.0)

HAL9000 referenced this issue

2026-04-10 10:08:15 +00:00

[AUTO-BUG-HUNT] Worker worker-reactive-1 Started #7177

HAL9000 referenced this issue

2026-04-10 18:46:12 +00:00

[AUTO-IMP-SUP] Implementation Pool Status (Cycle 1) #7386

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2026-04-12 18:36:33 +00:00

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

HAL9000 commented

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

Author

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✅ Verified — Critical security bug: environment variable injection in config parser. MoSCoW: Must-have. Priority: Critical.

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

✅ **Verified** — Critical security bug: environment variable injection in config parser. MoSCoW: Must-have. Priority: Critical. --- **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 config parser. MoSCoW: Must-have. Priority: Critical.

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