GitHub Advisoryadvisory · npm
GHSA-f886-m6hf-6m8v brace-expansion: Zero-step sequence causes process hang and memory exhaustion
MEDIUM
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
- https://github.com/juliangruber/brace-expansion/security/advisories/GHSA-f886-m6hf-6m8v web
- https://nvd.nist.gov/vuln/detail/CVE-2026-33750 advisory
- https://github.com/juliangruber/brace-expansion/issues/98 web
- https://github.com/juliangruber/brace-expansion/pull/95 web
- https://github.com/juliangruber/brace-expansion/pull/96 web
- https://github.com/juliangruber/brace-expansion/pull/97 web
- https://github.com/juliangruber/brace-expansion/commit/311ac0d54994158c0a384e286a7d6cbb17ee8ed5 web
- https://github.com/juliangruber/brace-expansion/commit/7fd684f89fdde3549563d0a6522226a9189472a2 web
- https://github.com/juliangruber/brace-expansion/commit/b9cacd9e55e7a1fa588fe4b7bb1159d52f1d902a web
- https://github.com/juliangruber/brace-expansion package
- https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113 web
- https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184 web