Eresus Python Audit

Python Security Audit

Purpose

Perform a comprehensive, depth-first security audit of Python codebases. This skill provides the complete knowledge of Bandit's 50+ security checks, organized by category and severity, plus framework-specific patterns for Django, Flask, FastAPI, and emerging ML/AI attack surfaces.

Use view_file and grep_search exclusively. No terminal commands.

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Audit Workflow

Phase 1: Reconnaissance

1. Identify the Python framework in use (Django, Flask, FastAPI, Tornado, aiohttp, raw stdlib)
2. Check requirements.txt / pyproject.toml / Pipfile for dangerous dependencies
3. Map entry points: URL routes, CLI commands, message consumers, scheduled tasks
4. Identify configuration files and secrets management approach

Phase 2: Systematic Check — By Category

Work through each category below. For each check, use grep_search to find all instances, then view_file to trace the data flow and confirm exploitability.

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B1xx — Miscellaneous Checks

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B101 | assert_used | Low | assert statements used for security checks (removed with -O flag) | | B102 | exec_used | Medium | exec() calls — trace if input is user-controlled | | B103 | set_bad_file_permissions | Medium | os.chmod() with overly permissive modes (0o777, 0o666) | | B104 | hardcoded_bind_all_interfaces | Medium | Binding to 0.0.0.0 — exposes service on all interfaces | | B105 | hardcoded_password_string | Low | Strings assigned to variables named password, secret, key, token | | B106 | hardcoded_password_funcarg | Low | Password-like strings passed as function arguments | | B107 | hardcoded_password_default | Low | Default parameter values containing password-like strings | | B108 | hardcoded_tmp_directory | Low | Hardcoded /tmp paths — race conditions, symlink attacks | | B109 | password_config_option_not_marked_secret | Low | Config options with password/secret that aren't marked as sensitive | | B110 | try_except_pass | Low | except: pass — silently swallowing errors including security exceptions | | B111 | execute_with_run_as_root_equals_true | Medium | Functions called with run_as_root=True | | B112 | try_except_continue | Low | except: continue — same problem as B110 | | B113 | request_without_timeout | Medium | requests.get/post() without timeout= parameter — DoS via hang |

Audit Depth for B1xx

• B101: Check if assert guards authentication or authorization. If so, HIGH severity.
• B102: Trace exec() input — if user-controlled, escalate to CRITICAL (RCE).
• B105/106/107: Check if the hardcoded credentials are for production systems or test fixtures.
• B113: Check all HTTP client calls (requests, httpx, urllib3, aiohttp) for timeout.

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B2xx — Application/Framework Misconfiguration

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B201 | flask_debug_true | High | app.run(debug=True) — enables Werkzeug debugger (RCE) | | B202 | tarfile_unsafe_members | High | tarfile.extractall() without filter= — path traversal via tar |

Audit Depth for B2xx

• B201: Check if debug=True is conditional on environment or always on. Check for WERKZEUG_DEBUG_PIN.
• B202: Any tarfile.open() + extractall() from user-uploaded files = CRITICAL path traversal.

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B3xx — Dangerous Function Calls (Blacklists)

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B324 | hashlib | Medium | Use of md5(), sha1() for security-sensitive operations (password hashing, integrity) |

Extended B3xx Checks (Eresus additions)

• hashlib.md5() / hashlib.sha1() for password storage → escalate to HIGH
• Use of random module instead of secrets for security tokens → HIGH
• string.Template with user input → potential template injection

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B5xx — Cryptography

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B501 | request_with_no_cert_validation | High | requests.get(url, verify=False) — TLS downgrade | | B502 | ssl_with_bad_version | High | ssl.SSLContext(ssl.PROTOCOL_SSLv2) or SSLv3 | | B503 | ssl_with_bad_defaults | Medium | SSLContext with insecure default protocol | | B504 | ssl_with_no_version | Medium | SSLContext created without explicit protocol | | B505 | weak_cryptographic_key | High | RSA < 2048 bits, DSA < 2048 bits, EC < 224 bits | | B506 | yaml_load | Medium | yaml.load() without Loader=SafeLoader — deserialization RCE | | B507 | ssh_no_host_key_verification | High | Paramiko set_missing_host_key_policy(AutoAddPolicy) | | B508 | snmp_insecure_version | Medium | SNMPv1/v2 without authentication | | B509 | snmp_weak_cryptography | Medium | SNMPv3 with weak crypto |

Audit Depth for B5xx

• B501: Check if cert pinning is used. If verify=False is in production code → CRITICAL.
• B506: This is a deserialization sink. If input comes from HTTP/file upload → CRITICAL RCE.

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B6xx — Injection

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B601 | paramiko_calls | Medium | Paramiko SSH command execution — trace if command is user-controlled | | B602 | subprocess_popen_with_shell_equals_true | High | subprocess.Popen(cmd, shell=True) — command injection | | B603 | subprocess_without_shell_equals_true | Low | subprocess.Popen(cmd) without shell — still check input | | B604 | any_other_function_with_shell_equals_true | Medium | Any function with shell=True parameter | | B605 | start_process_with_a_shell | High | os.system(), os.popen() — command injection | | B606 | start_process_with_no_shell | Low | os.execl(), os.execve() — still trace input | | B607 | start_process_with_partial_path | Low | Process started without full path — PATH hijacking | | B608 | hardcoded_sql_expressions | Medium | SQL strings built with + or % or f-strings | | B609 | linux_commands_wildcard_injection | High | Commands with * glob — wildcard injection (tar, chown, etc.) | | B610 | django_extra_used | Medium | Django QuerySet.extra() — raw SQL injection | | B611 | django_rawsql_used | Medium | Django RawSQL() — raw SQL injection | | B612 | logging_config_insecure_listen | Medium | logging.config.listen() — arbitrary code execution | | B613 | trojansource | High | Unicode bidirectional control characters — trojan source attack | | B614 | pytorch_load | High | torch.load() — uses pickle internally, RCE if untrusted | | B615 | huggingface_unsafe_download | High | HuggingFace model downloads without safety checks |

Audit Depth for B6xx

• B602/B605: Trace the command string backwards. If ANY part is user-controlled → CRITICAL RCE.
• B608: Check if the SQL is parameterized elsewhere. Raw f-string SQL = HIGH SQLi.
• B609: tar cf archive.tar * in /tmp with user-created files → argument injection.
• B614: torch.load() from user-uploaded model file → CRITICAL RCE via pickle.
• B615: ML model supply chain attack — check if trust_remote_code=True.

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B7xx — XSS / Template Injection

| ID | Name | Severity | What to Search | |----|------|----------|----------------| | B701 | jinja2_autoescape_false | High | jinja2.Environment(autoescape=False) — stored/reflected XSS | | B702 | use_of_mako_templates | Medium | Mako templates — no auto-escaping by default | | B703 | django_mark_safe | Medium | mark_safe(user_input) — bypasses Django auto-escaping | | B704 | markupsafe_markup_xss | Medium | Markup(user_input) — bypasses escaping |

Audit Depth for B7xx

• B701: If autoescape=False and template renders user input → CRITICAL XSS.
• B703: Trace what data is passed to mark_safe(). If user-controlled → HIGH XSS.

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Framework-Specific Deep Checks

Django

• Check ALLOWED_HOSTS configuration (empty = open redirect)
• Check CSRF_COOKIE_HTTPONLY, SESSION_COOKIE_SECURE, SECURE_BROWSER_XSS_FILTER
• Check for @csrf_exempt decorators on sensitive views
• Check DEBUG = True in production settings
• Check SECRET_KEY hardcoded or in version control
• Check MIDDLEWARE ordering (SecurityMiddleware should be first)
• Check AUTH_PASSWORD_VALIDATORS configuration

Flask

• Check SECRET_KEY generation (must be cryptographically random)
• Check app.run(debug=True) in production
• Check for @app.before_request authentication enforcement
• Check session cookie configuration (SESSION_COOKIE_SECURE, SESSION_COOKIE_HTTPONLY)
• Check file upload handling (werkzeug.utils.secure_filename)

FastAPI

• Check for missing input validation (Body(), Query(), Path() without constraints)
• Check CORS configuration (allow_origins=["*"])
• Check authentication dependency injection (missing Depends())
• Check FileResponse / StreamingResponse path traversal
• Check OAuth2 implementation (token validation, scope enforcement)

ML/AI Attack Surface

• torch.load() — pickle-based, RCE from untrusted models
• transformers.pipeline(trust_remote_code=True) — arbitrary code execution
• pickle.loads() in model serialization pipelines
• Prompt injection in LLM-based applications
• Model poisoning via untrusted training data

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Severity Matrix

| Confidence \ Severity | LOW | MEDIUM | HIGH | |----------------------|-----|--------|------| | HIGH | Info | Medium | Critical | | MEDIUM | Low | Medium | High | | LOW | Info | Low | Medium |

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Report Format

For each finding, report:

### [B-ID]: [Check Name]

**Severity**: [LOW/MEDIUM/HIGH/CRITICAL]
**Confidence**: [LOW/MEDIUM/HIGH]
**File**: [path]:[line]

**Vulnerable Code**:
[show the code]

**Data Flow**:
[source] → [intermediaries] → [sink]

**Impact**: [what an attacker achieves]
**Remediation**: [specific fix with code example]
**Bandit Reference**: B[xxx]

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Tooling Constraints

Use ONLY:

• view_file — read source code
• grep_search — find patterns across the codebase

Do NOT use any terminal commands.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: EresusSecurity
• Source: EresusSecurity/appsec-skills
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.