GHSA-f886-m6hf-6m8v
MEDIUMbrace-expansion: Zero-step sequence causes process hang and memory exhaustion
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
brace-expansion📦brace-expansion📦brace-expansion📦brace-expansionReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
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:
test() is one of
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | brace-expansion | ≥ 4.0.0&&< 5.0.5 | 5.0.5 |
| 📦npm | brace-expansion | ≥ 3.0.0&&< 3.0.2 | 3.0.2 |
| 📦npm | brace-expansion | ≥ 2.0.0&&< 2.0.3 | 2.0.3 |
| 📦npm | brace-expansion | all versions | 1.1.13 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for brace-expansion. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update brace-expansion to 5.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f886-m6hf-6m8v is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-f886-m6hf-6m8v is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-f886-m6hf-6m8v. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-f886-m6hf-6m8v in your dependencies?
O3 detects GHSA-f886-m6hf-6m8v across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.