GHSA-F886-M6HF-6M8V
Vulnerability from github – Published: 2026-03-26 18:29 – Updated: 2026-03-27 21:38
VLAI?
Summary
brace-expansion: Zero-step sequence causes process hang and memory exhaustion
Details
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.
Severity ?
6.5 (Medium)
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "brace-expansion"
},
"ranges": [
{
"events": [
{
"introduced": "4.0.0"
},
{
"fixed": "5.0.5"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "brace-expansion"
},
"ranges": [
{
"events": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.0.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "brace-expansion"
},
"ranges": [
{
"events": [
{
"introduced": "2.0.0"
},
{
"fixed": "2.0.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "brace-expansion"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.1.13"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33750"
],
"database_specific": {
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-26T18:29:42Z",
"nvd_published_at": "2026-03-27T15:16:57Z",
"severity": "MODERATE"
},
"details": "### Impact\n\nA 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.\n\nThe loop in question:\n\nhttps://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184\n\n`test()` is one of\n\nhttps://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113\n\nThe 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.\n\nThis 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.\n\n### Patches\n\n\nUpgrade to versions\n- 5.0.5+\n\nA step increment of 0 is now sanitized to 1, which matches bash behavior.\n\n### Workarounds\n\nSanitize strings passed to `expand()` to ensure a step value of `0` is not used.",
"id": "GHSA-f886-m6hf-6m8v",
"modified": "2026-03-27T21:38:55Z",
"published": "2026-03-26T18:29:42Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/security/advisories/GHSA-f886-m6hf-6m8v"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33750"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/issues/98"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/pull/95"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/pull/96"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/pull/97"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/commit/311ac0d54994158c0a384e286a7d6cbb17ee8ed5"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/commit/7fd684f89fdde3549563d0a6522226a9189472a2"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/commit/b9cacd9e55e7a1fa588fe4b7bb1159d52f1d902a"
},
{
"type": "PACKAGE",
"url": "https://github.com/juliangruber/brace-expansion"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113"
},
{
"type": "WEB",
"url": "https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "brace-expansion: Zero-step sequence causes process hang and memory exhaustion"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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