profullstack · CSTRSK · Aug 9, 2026
diff --git a/docs/VULNERABILITY_CATALOG.md b/docs/VULNERABILITY_CATALOG.md
@@ -7,12 +7,12 @@ from each file's header comment, so this page cannot drift from the source.
 
 ## Totals
 
-- **Test cases:** 62
-- **Expected detections:** 62
-- **`VULNERABLE:` markers:** 123 (individual lines a scanner should flag)
-- **`SAFE:` markers:** 73 (lines a scanner must not flag — the false-positive control group)
+- **Test cases:** 63
+- **Expected detections:** 63
+- **`VULNERABLE:` markers:** 124 (individual lines a scanner should flag)
+- **`SAFE:` markers:** 74 (lines a scanner must not flag — the false-positive control group)
 - **Languages:** 8 — dotenv, go, java, javascript, json, python, ruby, text
-- **CWE categories:** 46 — CWE-20, CWE-22, CWE-78, CWE-79, CWE-89, CWE-90, CWE-95, CWE-113, CWE-117, CWE-190, CWE-201, CWE-209, CWE-256, CWE-295, CWE-321, CWE-327, CWE-330, CWE-338, CWE-346, CWE-347, CWE-352, CWE-362, CWE-377, CWE-384, CWE-489, CWE-502, CWE-506, CWE-532, CWE-601, CWE-611, CWE-614, CWE-639, CWE-643, CWE-681, CWE-759, CWE-798, CWE-862, CWE-915, CWE-918, CWE-942, CWE-943, CWE-1236, CWE-1321, CWE-1333, CWE-1336, CWE-1357
+- **CWE categories:** 47 — CWE-20, CWE-22, CWE-78, CWE-79, CWE-89, CWE-90, CWE-95, CWE-113, CWE-117, CWE-190, CWE-201, CWE-209, CWE-256, CWE-295, CWE-300, CWE-321, CWE-327, CWE-330, CWE-338, CWE-346, CWE-347, CWE-352, CWE-362, CWE-377, CWE-384, CWE-489, CWE-502, CWE-506, CWE-532, CWE-601, CWE-611, CWE-614, CWE-639, CWE-643, CWE-681, CWE-759, CWE-798, CWE-862, CWE-915, CWE-918, CWE-942, CWE-943, CWE-1236, CWE-1321, CWE-1333, CWE-1336, CWE-1357
 
 ## How coverage is scored
 
@@ -71,6 +71,7 @@ counts as a detection. See `docs/SCANNER_INTEGRATION.md`.
 | Test case | File | CWE | Severity | Expected | Markers |
 |---|---|---|---|---|---|
 | CSV formula injection from untrusted spreadsheet cells | [`csv-formula-injection.py`](../vulns/python/csv-formula-injection.py) | CWE-1236 | medium | yes | 1 vuln / 1 safe |
+| DNS rebinding allows SSRF through hostname re-resolution | [`cwe-300-python.py`](../vulns/python/cwe-300-python.py) | CWE-300 | high | yes | 1 vuln / 1 safe |
 | Excessive user-record exposure in an API response | [`excessive-data-exposure.py`](../vulns/python/excessive-data-exposure.py) | CWE-201 | high | yes | 1 vuln / 1 safe |
 | Flask debug mode enabled in application configuration | [`flask-debug-enabled.py`](../vulns/python/flask-debug-enabled.py) | CWE-489 | high | yes | 1 vuln / 1 safe |
 | Hardcoded secret used to configure session signing | [`hardcoded-session-secret.py`](../vulns/python/hardcoded-session-secret.py) | CWE-798 | high | yes | 1 vuln / 1 safe |

diff --git a/vulns/VULNERABILITY_CATALOG.json b/vulns/VULNERABILITY_CATALOG.json
@@ -2,10 +2,10 @@
   "schema": "threatcrush-testbed-catalog/1",
   "note": "Generated by scripts/generate-catalog.py \u2014 do not edit by hand.",
   "totals": {
-    "test_cases": 62,
-    "expected_detections": 62,
-    "vulnerable_markers": 123,
-    "safe_markers": 73,
+    "test_cases": 63,
+    "expected_detections": 63,
+    "vulnerable_markers": 124,
+    "safe_markers": 74,
     "languages": [
       "dotenv",
       "go",
@@ -40,6 +40,7 @@
       "CWE-209",
       "CWE-256",
       "CWE-295",
+      "CWE-300",
       "CWE-321",
       "CWE-327",
       "CWE-330",
@@ -791,6 +792,29 @@
         40
       ]
     },
+    {
+      "id": "py-dns-rebinding-ssrf",
+      "file": "vulns/python/cwe-300-python.py",
+      "title": "DNS rebinding allows SSRF through hostname re-resolution",
+      "category": "python",
+      "language": "python",
+      "cwe": "CWE-300",
+      "cwes": [
+        "CWE-300"
+      ],
+      "severity": "high",
+      "expected_detection": true,
+      "description": "The application resolves a user-supplied hostname twice: once for",
+      "detection_target": "Taint flow from request input into socket.getaddrinfo or",
+      "safe_guard": "The entire fixture is wrapped in `if False:` and cannot execute. It",
+      "attribution": "line",
+      "vulnerable_lines": [
+        33
+      ],
+      "safe_lines": [
+        44
+      ]
+    },
     {
       "id": "py-excessive-data-exposure",
       "file": "vulns/python/excessive-data-exposure.py",

diff --git a/vulns/python/cwe-300-python.py b/vulns/python/cwe-300-python.py
@@ -0,0 +1,45 @@
+"""
+@id py-dns-rebinding-ssrf
+@test-case DNS rebinding allows SSRF through hostname re-resolution
+@cwe CWE-300
+@severity high
+@language python
+@expected-detection true
+@description The application resolves a user-supplied hostname twice: once for
+             validation and once for the actual request. An attacker can use
+             DNS rebinding to pass validation with a safe IP, then have the
+             second resolution point to an internal address, enabling SSRF.
+@safe-guard The entire fixture is wrapped in `if False:` and cannot execute. It
+            uses only example.com and .invalid domains and makes no network
+            connections.
+@detection-target Taint flow from request input into socket.getaddrinfo or
+                  urllib.request.urlopen without pinning the resolved IP
+                  address.
+
+NEVER RUN IN PRODUCTION - intentional test case for scanner validation.
+"""
+
+
+if False:
+    import socket
+    import urllib.request
+
+    def fetch_url_vulnerable(request):
+        hostname = request.args.get("url")  # SOURCE: attacker-controlled
+        # First resolution for validation
+        ip = socket.gethostbyname(hostname)
+        if not ip.startswith("10.") and not ip.startswith("192.168."):
+            # Second resolution happens inside urlopen - vulnerable to rebinding
+            response = urllib.request.urlopen(f"http://{hostname}/internal")  # VULNERABLE: CWE-300
+            return response.read()
+        return "blocked"
+
+    def fetch_url_safe(request):
+        hostname = request.args.get("url")
+        # Resolve once and pin the IP
+        ip = socket.gethostbyname(hostname)
+        if ip.startswith("10.") or ip.startswith("192.168."):
+            return "blocked"
+        # Use the resolved IP directly, not the hostname
+        response = urllib.request.urlopen(f"http://{ip}/internal", headers={"Host": hostname})  # SAFE: IP is pinned
+        return response.read()  # @expected-detection false