Summary
undici vulnerable to Denial of Service via orphaned RetryHandler response body
Workarounds
Impose an independent request deadline and destroy the response body when it expires. bodyTimeout alone does not prevent this.
Impact
undici's RetryHandler can leave a response body pending indefinitely. When a retried request receives a non-retryable response after a truncated one, the original response.body held by the application is never settled, so reads such as response.body.text() hang and bodyTimeout does not fire. A malicious server can repeat this to accumulate pending promises and streams, leading to denial of service.
CVE-2026-18149 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (7.29.1, 8.10.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Patched in undici v7.29.1 and v8.10.2.
Frequently Asked Questions
- What is CVE-2026-18149? CVE-2026-18149 is a medium-severity security vulnerability in undici (npm), affecting versions >= 7.11.0, < 7.29.1. It is fixed in 7.29.1, 8.10.2.
- How severe is CVE-2026-18149? CVE-2026-18149 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of undici are affected by CVE-2026-18149? undici (npm) versions >= 7.11.0, < 7.29.1 is affected.
- Is there a fix for CVE-2026-18149? Yes. CVE-2026-18149 is fixed in 7.29.1, 8.10.2. Upgrade to this version or later.
- Is CVE-2026-18149 exploitable, and should I be worried? Whether CVE-2026-18149 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-18149 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-18149?
- Upgrade
undicito 7.29.1 or later - Upgrade
undicito 8.10.2 or later
- Upgrade