GitHub Advisoryadvisory · npm

GHSA-f886-m6hf-6m8v brace-expansion: Zero-step sequence causes process hang and memory exhaustion

MEDIUM Published 2026-03-26 Modified 2026-03-27 Official page ↗
Aliases
CVE-2026-33750
Ecosystem
npm
Packages
brace-expansion
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Weaknesses
CWE-400
Reviewed
2026-03-26

Affected packages

• npm brace-expansion: >= 4.0.0, < 5.0.5 → fixed in 5.0.5 • npm brace-expansion: >= 3.0.0, < 3.0.2 → fixed in 3.0.2 • npm brace-expansion: >= 2.0.0, < 2.0.3 → fixed in 2.0.3 • npm brace-expansion: < 1.1.13 → fixed in 1.1.13

Description

Impact 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. Patches Upgrade to versions • 5.0.5+ A step increment of 0 is now sanitized to 1, which matches bash behavior. Workarounds Sanitize strings passed to `expand()` to ensure a step value of `0` is not used.

Related

Alias · CVE (1)

  • CVE-2026-33750 The brace-expansion library generates arbitrary strings containing a common prefix and suffix. vulnerability

Weakness · CWE (1)

  • CWE-400 Uncontrolled Resource Consumption weakness

References