CVE-2026-45149 is a medium-severity (CVSS 6.5) Uncontrolled Resource Consumption vulnerability in brace-expansion. A fix is available for brace-expansion — see the affected versions and patch details below.
brace-expansion: Large numeric range defeats documented `max` DoS protection
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45149.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-45149 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
brace-expansionnpmDescription
The brace-expansion library generates arbitrary strings containing a common prefix and suffix. From 5.0.0 to before 5.0.6, the max option was being applied too late. When expanding a single large numeric range like {1..10000000}, the sequence generation loop generates all 10 million intermediate elements before the max limit is applied With max=10, the output is correctly limited to 10 items, but the process still allocates ~505 MB and spends ~800ms building the full intermediate array. This vulnerability is fixed in 5.0.6.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | brace-expansion | ≥ 5.0.0&&< 5.0.6 | 5.0.6npm install brace-expansion@5.0.6 |
Affected Products
brace-expansionjuliangruberDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for brace-expansion, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update brace-expansion to 5.0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45149 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat products ship brace-expansion versions 1.x and 2.x, which are not affected by this vulnerability. The flaw exists only in versions 5.0.0 through 5.0.5.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-45149 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Hardened Images | nodejs24-main-24.15.0-1.hum1 | RHSA-2026:13874 |
| Red Hat Hardened Images | dotnet8-0-main-8.0.127-1.hum1 | RHSA-2026:17682 |
| Red Hat Hardened Images | nodejs26-main-26.3.0-1.2.hum1 | RHSA-2026:22380 |
| Red Hat Hardened Images | rust-main-1.96.0-1.hum1 | RHSA-2026:22934 |
| Red Hat Hardened Images | llvm21-main-21.1.8-6.hum1 | RHSA-2026:24069 |
| Red Hat Hardened Images | nodejs25-main-25.9.0-1.1.hum1 | RHSA-2026:7378 |
| Red Hat Hardened Images | nodejs22-main-22.22.0-1.3.hum1 | RHSA-2026:7387 |
| Red Hat Hardened Images | llvm-main-21.1.8-1.1.hum1 | RHSA-2026:7634 |
Frequently Asked Questions
Is CVE-2026-45149 in your dependencies?
Find it across npm, including transitive dependencies.