CVE-2026-13149 juliangruber CVE debrief

Who should care

Users of brace-expansion through 5.0.6, operators, platform administrators, vulnerability management teams, and security teams should be aware of this denial of service vulnerability. The expand() function's exponential-time complexity can cause significant CPU consumption and event-loop blocking when processing crafted strings.

Technical summary

The CVE-2026-13149 vulnerability affects brace-expansion through 5.0.6. The expand() function exhibits exponential-time complexity in the number of consecutive non-expanding '{}' brace groups. An attacker can cause significant CPU consumption and event-loop blocking by passing a crafted string to expand(), directly or transitively. The max option does not mitigate this issue as it bounds the output size rather than the recursion work. Users of brace-expansion should be aware of this denial of service vulnerability.

Defensive priority

High priority should be given to updating brace-expansion to a version beyond 5.0.6 to prevent potential denial of service attacks. Additionally, validating and sanitizing input strings, implementing monitoring, and applying compensating controls can help mitigate the vulnerability.

Recommended defensive actions

• Update brace-expansion to a version beyond 5.0.6
• Validate and sanitize input strings to prevent crafted inputs
• Implement monitoring to detect potential CPU consumption and event-loop blocking
• Consider applying compensating controls to limit the impact of potential attacks
• Review relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD detail provide information on the vulnerability. However, further analysis is required to fully understand the affected scope and potential impact. The expand() function's exponential-time complexity can cause significant CPU consumption and event-loop blocking when processing crafted strings. Users should verify their deployments and review official advisories for affected scope and vendor guidance.

Official resources