CVE-2025-69871 identifies a race condition vulnerability in the MedusaJS e-commerce platform, specifically affecting version 2.12.2 and earlier. The flaw exists in the registerUsage() function within the promotion module, which is responsible for enforcing usage limits on promotional codes. The vulnerability stems from a non-atomic sequence of operations: the function reads the current usage count, checks it against the allowed limit, and then updates the count. Because these steps are not performed atomically, concurrent checkout requests can exploit this timing gap to bypass usage limits. An attacker can send multiple simultaneous checkout requests using the same promotional code, causing the system to incorrectly allow more redemptions than intended. This can lead to unlimited use of limited-use promotions, resulting in financial losses for merchants. The vulnerability requires no authentication or user interaction but has a high attack complexity due to the need to coordinate concurrent requests precisely. The CVSS v3.1 score of 8.1 reflects the high impact on confidentiality, integrity, and availability, as well as the network attack vector and lack of privileges required. While no public exploits are known, the vulnerability represents a significant risk to organizations relying on MedusaJS for their e-commerce operations, particularly those heavily dependent on promotional campaigns. The underlying issue is a classic example of CWE-362 (Race Condition), highlighting the importance of atomic operations in concurrent environments.

The primary impact of CVE-2025-69871 is financial loss due to unauthorized unlimited redemption of limited-use promotional codes. This undermines the integrity of promotional campaigns, potentially causing significant revenue leakage and damaging merchant trust. The vulnerability also affects availability indirectly by potentially overwhelming backend systems with fraudulent transactions. Confidentiality is impacted as the attacker can manipulate transaction data and usage counts. Organizations relying on MedusaJS for e-commerce may face reputational damage, customer dissatisfaction, and increased operational costs to investigate and remediate fraudulent activities. The ease of exploitation without authentication increases the threat level, especially for high-traffic online stores where concurrent checkout attempts can be automated. The scope includes all deployments of vulnerable MedusaJS versions using the promotion module with usage limits, which may be widespread given MedusaJS's growing adoption in modern e-commerce platforms.

To mitigate CVE-2025-69871, organizations should immediately upgrade MedusaJS to a version where this race condition is fixed once available. In the absence of an official patch, implement concurrency controls such as database-level locking or atomic transactions around the registerUsage() function to ensure the read-check-update sequence is atomic. Employ rate limiting and request throttling on checkout endpoints to reduce the feasibility of concurrent exploitation attempts. Monitor logs for unusual patterns of promotional code usage, especially rapid or simultaneous redemptions. Consider implementing additional server-side validation to cross-check usage counts before finalizing transactions. Engage with the MedusaJS community or maintainers to track patch releases and security advisories. Finally, conduct thorough testing of promotion modules under concurrent load to detect similar race conditions proactively.