GHSA-f886-m6hf-6m8v CVE-2026-33750
brace-expansion: Zero-step sequence causes process hang and memory exhaustion
- Severity
- 6.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.45%
- Chance of exploitation in the next 30 days. Higher than 38.91% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-400 Uncontrolled Resource Consumption
- Fix
5.0.5- Upgrade brace-expansion to this version or later
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 versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| brace-expansion | >= 4.0.0, < 5.0.5 |
5.0.5 |
| brace-expansion | >= 3.0.0, < 3.0.2 |
3.0.2 |
| brace-expansion | >= 2.0.0, < 2.0.3 |
2.0.3 |
| brace-expansion | < 1.1.13 |
1.1.13 |
| brace-expansion | >= 4.0.0, < 5.0.5 |
5.0.5 |
| brace-expansion | >= 3.0.0, < 3.0.2 |
3.0.2 |
| brace-expansion | >= 2.0.0, < 2.0.3 |
2.0.3 |
| brace-expansion | < 1.1.13 |
1.1.13 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
brace-expansion npm → 5.0.5
- npm
npm install brace-expansion@5.0.5- yarn
yarn add brace-expansion@5.0.5- pnpm
pnpm add brace-expansion@5.0.5
Severity breakdown
CVSS 3.1 6.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Advisories
Fixes and patches
- github.com/juliangruber/brace-expansion/pull/95
- github.com/juliangruber/brace-expansion/pull/96
- github.com/juliangruber/brace-expansion/pull/97
- github.com/juliangruber/brace-expansion/commit/311ac0d54994158c0a384e286a7d6cbb…
- github.com/juliangruber/brace-expansion/commit/7fd684f89fdde3549563d0a6522226a9…
- github.com/juliangruber/brace-expansion/commit/b9cacd9e55e7a1fa588fe4b7bb1159d5…
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-qhr7-859c-m2p7 brace-expansion: DoS via uncontrolled recursion on nested brace groups causing stack exhaustion | High | Also affects brace-expansion |
| GHSA-q2hr-2g5m-vwhr brace-expansion: Quadratic-time expansion of the `{a},b}` rewrite causes CPU denial of service | Medium | Also affects brace-expansion |
| GHSA-6j4f-fj2g-mc7p brace-expansion: DoS via uncontrolled recursion in parseCommaParts causing stack exhaustion | High | Also affects brace-expansion |
| GHSA-rgw5-rvv9-x895 brace-expansion: DoS via unbounded intermediate arrays, bypassing the CVE-2026-14257 mitigation | High | Also affects brace-expansion |
| GHSA-mh99-v99m-4gvg brace-expansion: DoS via unbounded expansion length causing an out-of-memory process crash | High | Also affects brace-expansion |
| GHSA-3jxr-9vmj-r5cp brace-expansion: DoS via exponential-time expansion of consecutive non-expanding {} groups | High | Also affects brace-expansion |
| GHSA-jxxr-4gwj-5jf2 brace-expansion: Large numeric range defeats documented `max` DoS protection | High | Also affects brace-expansion |
| GHSA-v6h2-p8h4-qcjw brace-expansion Regular Expression Denial of Service vulnerability | Low | Also affects brace-expansion |
Credits: katzj, navgarcha, subhashdasyam
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