The vulnerability identified as CVE-2026-3449 affects the @tootallnate/once package, a JavaScript utility commonly used to ensure a function is only executed once. Versions prior to 3.0.1 contain a flaw in the handling of promises when combined with the AbortSignal option. AbortSignal is a standard mechanism to abort asynchronous operations. In this case, if the AbortSignal triggers an abort, the promise does not resolve or reject but instead remains in a permanently pending state. This incorrect control flow scoping means that any code awaiting the promise or chaining .then() handlers will hang indefinitely. The root cause is improper cleanup or state transition logic when the abort event occurs, leading to a control-flow leak. This can cause significant issues in applications relying on timely promise resolution, including stalled HTTP requests, blocked event loop or worker threads, and overall degraded availability. The vulnerability requires local access with low privileges and no user interaction, indicating it is exploitable in scenarios where an attacker can trigger abort signals internally. The CVSS 4.8 score reflects medium severity, primarily due to the impact on availability and the limited attack vector. No known exploits have been reported, and no patches are linked in the provided data, but upgrading to version 3.0.1 or later is recommended to resolve the issue.

The primary impact of CVE-2026-3449 is on application availability and reliability. Applications using the vulnerable @tootallnate/once package in asynchronous workflows that utilize AbortSignal may experience indefinite hangs on promises, leading to stalled requests and blocked worker threads. This can degrade user experience, cause timeouts, and potentially lead to denial of service conditions if critical asynchronous operations never complete. For organizations running high-availability services or real-time systems, this can translate into service disruptions and operational challenges. While confidentiality and integrity are not directly affected, the availability degradation can indirectly impact business continuity and customer trust. The vulnerability is particularly concerning in environments with heavy asynchronous processing, such as web servers, microservices, or serverless functions. Since exploitation requires local access with low privileges, attackers or malicious insiders with limited access could trigger the issue to disrupt service. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed proactively to prevent future abuse.

To mitigate CVE-2026-3449, organizations should upgrade the @tootallnate/once package to version 3.0.1 or later, where the issue has been resolved. If immediate upgrading is not feasible, developers should audit their use of AbortSignal with this package and implement timeout or fallback mechanisms to detect and recover from indefinitely pending promises. Adding monitoring to detect stalled asynchronous operations can help identify exploitation attempts or accidental hangs. Avoid relying solely on AbortSignal for critical control flow without additional safeguards. In environments where local access cannot be fully controlled, restrict permissions to limit the ability to trigger abort signals maliciously. Additionally, conduct code reviews and testing focused on promise handling and abort scenarios to ensure robust error and state management. Finally, maintain awareness of updates from the package maintainers and apply patches promptly.