CVE-2026-93749: source-map-js through 1.2.1 Event Loop Denial of Service
source-map-js through 1.2.1 fails to validate the per-section offset line value in indexed source maps, allowing attackers to specify arbitrary numeric values. Attackers can supply extremely large offset line values that cause synchronous event loop blocking for extended periods, preventing the service from handling other requests.
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed to exploitation?
Deployments using npm/source-map-js version 1.2.1 or earlier are affected if an attacker can supply an indexed source map that the service processes.
What does an attacker need to cause the denial of service?
No privileges or user interaction are required. The attacker needs to provide an indexed source map containing an extremely large per-section offset line value.
What is the operational impact of a successful attack?
Processing the crafted value can synchronously block the event loop for an extended period, preventing the service from handling other requests.