Vulnerability-Lookup

GHSA-3JXR-9VMJ-R5CP

Vulnerability from github – Published: 2026-07-20 20:51 – Updated: 2026-07-20 20:51

Summary

brace-expansion: DoS via exponential-time expansion of consecutive non-expanding {} groups

Details

Summary

brace-expansion's expand() exhibits exponential-time - O(2ⁿ) - behavior in the number of consecutive non-expanding {} groups. A short, all-ASCII input (~90 bytes/30 groups) blocks the calling thread for minutes; a slightly longer input hangs it effectively indefinitely. Because the dominant consumers run on Node's single-threaded event loop, one small input can fully stall a worker/process.

In expand_, post is computed unconditionally at the top of the function, before the early-return branches that don't use it:

const post = m.post.length ? expand_(m.post, max, false) : [''];   // always recurses
  ...
if (!isSequence && !isOptions) {
  if (m.post.match(/,(?!,).*\}/)) {
    str = m.pre + '{' + m.body + escClose + m.post;
    return expand_(str, max, true); // restart — `post` discarded
  }
  return [str];
}

For input like a{},{},…, the first {} is non-expanding, so control reaches the {a},b} rewrite branch - but expand_ has already recursed into post over the entire remaining tail, only to throw the result away. Each level therefore spawns two recursive expansions over essentially the same remaining work: T(n) = 2·T(n−1) ⇒ O(2ⁿ).

The max option does not mitigate this: max only bounds the output-building loops; neither the post recursion nor the rewrite recursion consults it.

Measured on 5.0.6:

groups (n)	input bytes	time
20	60	130 ms
24	72	1.9 s
26	78	7.8 s
30 (PoC)	90	~2 min

Proof of concept

const { expand } = require('brace-expansion');
// 30 non-expanding groups, ~90 bytes — blocks for minutes:
expand('a{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{}');

Impact

Any application that passes attacker-influenced strings to brace-expansion.expand() - directly or transitively via minimatch/glob brace patterns - can be driven into a multi-minute-to-indefinite CPU hang by a tiny request, denying service on that thread/process.

Remediation

Upgrade to a patched release. The fix: 1. Defers computing post until after the early-return branches (and computes it locally in the $-suffix branch), so post is only expanded when a brace set actually expands and the value is used. This alone removes the exponential. 1. Converts the {a},b} rewrite from recursion to an in-function loop, so a long run of rewrites cannot grow the call stack.

Verified: the PoC drops from ~2 min to 0.55 ms, 5,000 groups complete in ~344 ms, and output is identical to 5.0.6 across a behavioral-equivalence suite (sequences, padding, $-prefix, a{},b}c, {},a}b, x{{a,b}}y, etc.). Post-fix complexity is ~O(n²) on this input class - acceptable for the security fix; a linear rewrite can be a non-urgent follow-up.

If immediate upgrade isn't possible, avoid passing untrusted input to expand() / glob brace patterns, or run such expansion under a timeout/worker.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

7.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/S:N/AU:Y/R:U/V:D/RE:M/U:Amber

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "brace-expansion"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "5.0.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "brace-expansion"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.1.16"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "brace-expansion"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-13149"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-407"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T20:51:09Z",
    "nvd_published_at": "2026-06-30T10:16:34Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nbrace-expansion\u0027s expand() exhibits exponential-time - O(2\u207f) - behavior in the number of consecutive non-expanding {} groups. A short, all-ASCII input (~90 bytes/30 groups) blocks the calling thread for minutes; a slightly longer input hangs it effectively indefinitely. Because the dominant consumers run on Node\u0027s single-threaded event loop, one small input can fully stall a worker/process.\n\nIn `expand_`, `post` is computed unconditionally at the top of the function, before the early-return branches that don\u0027t use it:\n```js\nconst post = m.post.length ? expand_(m.post, max, false) : [\u0027\u0027];   // always recurses\n  ...\nif (!isSequence \u0026\u0026 !isOptions) {\n  if (m.post.match(/,(?!,).*\\}/)) {\n    str = m.pre + \u0027{\u0027 + m.body + escClose + m.post;\n    return expand_(str, max, true); // restart \u2014 `post` discarded\n  }\n  return [str];\n}\n```\n\nFor input like a{},{},\u2026, the first {} is non-expanding, so control reaches the {a},b} rewrite branch - but `expand_` has already recursed into post over the entire remaining tail, only to throw the result away.\nEach level therefore spawns two recursive expansions over essentially the same remaining work: `T(n) = 2\u00b7T(n\u22121) \u21d2 O(2\u207f)`.\n\nThe max option does not mitigate this: max only bounds the output-building loops; neither the post recursion nor the rewrite recursion consults it.\n  \nMeasured on 5.0.6:\n\n| groups (n) | input bytes | time |\n|---|---|---|\n| 20 | 60 | 130 ms |\n| 24 | 72 | 1.9 s |\n| 26 | 78 | 7.8 s |\n| 30 (PoC) | 90 | ~2 min |\n\n### Proof of concept\n```js\nconst { expand } = require(\u0027brace-expansion\u0027);\n// 30 non-expanding groups, ~90 bytes \u2014 blocks for minutes:\nexpand(\u0027a{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{}\u0027);\n```\n\n### Impact\n\nAny application that passes attacker-influenced strings to brace-expansion.expand() - directly or transitively via minimatch/glob brace patterns - can be driven into a multi-minute-to-indefinite CPU hang by a tiny request, denying service on that thread/process.\n\n### Remediation\n\nUpgrade to a patched release. The fix:\n1. Defers computing post until after the early-return branches (and computes it locally in the $-suffix branch), so post is only expanded when a brace set actually expands and the value is used. This alone removes the exponential.\n1. Converts the {a},b} rewrite from recursion to an in-function loop, so a long run of rewrites cannot grow the call stack.\n\nVerified: the PoC drops from ~2 min to 0.55 ms, 5,000 groups complete in ~344 ms, and output is identical to 5.0.6 across a behavioral-equivalence suite (sequences, padding, $-prefix, a{},b}c, {},a}b, x{{a,b}}y, etc.). Post-fix complexity is ~O(n\u00b2) on this input class - acceptable for the security fix; a linear rewrite can be a non-urgent follow-up.\n\nIf immediate upgrade isn\u0027t possible, avoid passing untrusted input to expand() / glob brace patterns, or run such expansion under a timeout/worker.",
  "id": "GHSA-3jxr-9vmj-r5cp",
  "modified": "2026-07-20T20:51:10Z",
  "published": "2026-07-20T20:51:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/security/advisories/GHSA-3jxr-9vmj-r5cp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-13149"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/pull/122"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/pull/123"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/commit/835d6be91201122d9adffb0c0c8c094189ace265"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/commit/c7e33ec13ac1a684c116720843ce24e208611754"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/commit/d74e63030c012e3b7ae81657b8d665619cd51b95"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/juliangruber/brace-expansion"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/releases/tag/v1.1.16"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/releases/tag/v2.1.2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/juliangruber/brace-expansion/releases/tag/v5.0.7"
    },
    {
      "type": "WEB",
      "url": "https://www.npmjs.com/package/brace-expansion"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/S:N/AU:Y/R:U/V:D/RE:M/U:Amber",
      "type": "CVSS_V4"
    }
  ],
  "summary": "brace-expansion: DoS via exponential-time expansion of consecutive non-expanding {} groups"
}

CVE-2026-13149 (GCVE-0-2026-13149)

Vulnerability from cvelistv5 – Published: 2026-06-30 08:30 – Updated: 2026-07-08 11:38

Summary

brace-expansion through 5.0.6 is vulnerable to denial of service. The expand() function exhibits exponential-time complexity in the number of consecutive non-expanding '{}' brace groups. An attacker who passes a crafted string to expand(), directly or transitively, can cause significant CPU consumption and event-loop blocking. The max option does not mitigate this, as it bounds the output size rather than the recursion work.

Severity

7.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/S:N/AU:Y/R:U/V:D/RE:M/U:Amber

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-400 - Uncontrolled Resource Consumption
CWE-407 - Inefficient Algorithmic Complexity

Assigner

seal

References

2 references

URL	Tags
https://github.com/juliangruber/brace-expansion/c…
https://www.npmjs.com/package/brace-expansion

Impacted products

1 product

Vendor	Product	Version
juliangruber	brace-expansion	Affected: 0 , ≤ 5.0.6 (semver)

Credits

bnbdr

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date	Other

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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-3JXR-9VMJ-R5CP

Summary

Proof of concept

Impact

Remediation

CVE-2026-13149 (GCVE-0-2026-13149)

Tags

Sightings

Nomenclature