CVE-2026-33750

Workarounds

Sanitize strings passed to expand() to ensure a step value of 0 is not used.

A brace pattern with a zero step value (e.g., {1..2..0}) causes the sequence generation loop to run indefinitely, making the process hang for seconds and allocate heaps of memory.

The loop in question:

https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184

test() is one of

https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113

The increment is computed as Math.abs(0) = 0, so the loop variable never advances. On a test machine, the process hangs for about 3.5 seconds and allocates roughly 1.9 GB of memory before throwing a RangeError. Setting max to any value has no effect because the limit is only checked at the output combination step, not during sequence generation.

This affects any application that passes untrusted strings to expand(), or by error sets a step value of 0. That includes tools built on minimatch/glob that resolve patterns from CLI arguments or config files. The input needed is just 10 bytes.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-33750 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.0.5, 3.0.2, 2.0.3, 1.1.13); upgrading removes the vulnerable code path.

Kodem intelligence

Upgrade to versions

• 5.0.5+

A step increment of 0 is now sanitized to 1, which matches bash behavior.

1. What is CVE-2026-33750? CVE-2026-33750 is a medium-severity uncontrolled resource consumption vulnerability in brace-expansion (npm), affecting versions >= 4.0.0, < 5.0.5. It is fixed in 5.0.5, 3.0.2, 2.0.3, 1.1.13. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-33750? CVE-2026-33750 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of brace-expansion are affected by CVE-2026-33750? brace-expansion (npm) versions >= 4.0.0, < 5.0.5 is affected.
4. Is there a fix for CVE-2026-33750? Yes. CVE-2026-33750 is fixed in 5.0.5, 3.0.2, 2.0.3, 1.1.13. Upgrade to this version or later.
5. Is CVE-2026-33750 exploitable, and should I be worried? Whether CVE-2026-33750 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-33750 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-33750?
   • Upgrade brace-expansion to 5.0.5 or later
   • Upgrade brace-expansion to 3.0.2 or later
   • Upgrade brace-expansion to 2.0.3 or later
   • Upgrade brace-expansion to 1.1.13 or later