What’s Vulnerable › Vulnerabilities

CVE-2026-102277: brace-expansion: Quadratic-time expansion of the `{a},b}` rewrite causes CPU denial of service

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-28 · updated 2026-09-30
• Weakness: CWE-400

Description

The brace-expansion library generates arbitrary strings containing a common prefix and suffix. Prior to 1.1.21, 2.1.7, 3.0.9, and 5.0.12, the expand function handles untrusted {a},b}-shaped patterns with many trailing closing braces by restarting its scan once for each trailing closing brace. The successive full-input rescans with linear working-string growth cause quadratic CPU time and memory pressure that can block the Node.js event loop. The process eventually recovers, making the impact a recoverable CPU denial of service. This issue is fixed in versions 1.1.21, 2.1.7, 3.0.9, and 5.0.12.

Affected products

• Npm Brace-Expansion: from 4.0.0 before 5.0.12; from 3.0.0 before 3.0.9; from 2.0.0 before 2.1.7; before 1.1.21 — fixed in 5.0.12, 3.0.9, 2.1.7, 1.1.21
• juliangruber brace-expansion: from 4.0.0, < 5.0.12; from 3.0.0, < 3.0.9; from 2.0.0, < 2.1.7; before 1.1.21

How to fix

Upgrade to a fixed version: Npm Brace-Expansion 5.0.12, 3.0.9, 2.1.7, 1.1.21. Check the vendor advisory for mitigations.

References

• https://github.com/juliangruber/brace-expansion/commit/33a5ef17b8d800bbfa8c52b14c39043b6aac1a96
• https://github.com/juliangruber/brace-expansion/commit/bdff773f98e5988616b7039cc9b508df5d640b22
• https://github.com/juliangruber/brace-expansion/commit/c55e67d8d8b1c56a2474afff15c2891166b2d364
• https://github.com/juliangruber/brace-expansion/commit/ffdfa3e3806bed17c0874b8f1439b084de354a7e
• https://github.com/juliangruber/brace-expansion/security/advisories/GHSA-q2hr-2g5m-vwhr

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