CVE-2026-116215 in MacCMS
Summary
by MITRE • 10/26/2026
MacCMS v10 through 2026.1000.4056 contains a race condition vulnerability in Card::useData() that allows authenticated members to redeem one recharge card multiple times via the user/buy endpoint. Attackers can send many concurrent flag=card requests that pass the non-locking card read before it is marked used, inflating user_points to buy VIP upgrades and paid content.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified in MacCMS versions 10 through 2026.1000.4056 represents a critical race condition within the application logic responsible for processing recharge card redemptions. Specifically, the flaw resides in the Card::useData() method which handles requests routed to the user/buy endpoint. This function is designed to validate and consume single-use authentication tokens or credit vouchers that users purchase to enhance their account status. The core technical deficiency lies in the lack of atomic operations when checking the validity of a card against its usage status. When an authenticated member initiates a redemption request by sending a flag=card parameter, the system performs a read operation to verify if the card is available for use but fails to implement any locking mechanism or database-level transaction isolation during this check-to-use interval. This creates a time-of-check to time-of-use (TOCTOU) window where multiple concurrent requests can simultaneously pass the initial validation step before either request updates the card's status to used in the backend storage.
From an operational perspective, this race condition allows malicious actors with valid user accounts to exploit the concurrency gap by flooding the server with numerous simultaneous redemption attempts for a single recharge card. Because each thread or process sees the card as unused at the moment of its individual check, all requests are processed successfully rather than being rejected after the first successful redemption. This results in the artificial inflation of user_points associated with the attacker's account without corresponding financial expenditure. The immediate impact is economic fraud and resource abuse, as attackers can leverage these illegitimately acquired points to upgrade their membership status to VIP tiers or access premium content that would otherwise require payment. This not only causes direct revenue loss for the platform but also degrades service quality by allowing unauthorized users to consume paid resources at no cost.
The security implications extend beyond simple financial fraud, as gaining elevated privileges through this method can potentially lead to further exploitation vectors depending on what actions VIP status or high point balances enable within the MacCMS ecosystem. For instance, if higher privilege levels allow for administrative features, content manipulation, or API access restrictions bypasses, the initial race condition could serve as a stepping stone for more severe compromises such as unauthorized data modification or system takeover. The vulnerability aligns with CWE-362, which classifies concurrent execution using shared resources without proper synchronization, and is also relevant to CWE-841 regarding improper enforcement of flow control in multi-threaded environments. In the context of the MITRE ATT&CK framework, this behavior corresponds to Tactic TA0005 (Defense Evasion) or potentially TA0006 (Credential Access/Privilege Escalation) depending on how the inflated points are utilized to bypass access controls.
To mitigate this vulnerability, developers must enforce atomicity in the card redemption process at the database level rather than relying solely on application-level checks. Implementing a unique constraint combined with an update query that includes a condition checking for unused status ensures that only one transaction can succeed per card ID. For example, using SQL statements like UPDATE cards SET is_used = true WHERE id = ? AND is_used = false will return the number of affected rows; if zero rows are updated, it indicates another process has already consumed the card. Additionally, introducing server-side rate limiting on the user/buy endpoint can reduce the likelihood of successful race condition exploitation by throttling rapid successive requests from a single session or IP address. Regular security audits focusing on transactional integrity and concurrency handling in financial logic modules are essential to prevent similar issues in other parts of the application infrastructure.