Summary
Internationalized Domain Names in Applications (IDNA) vulnerable to denial of service from specially crafted inputs to idna.encode
Workarounds
Domain names cannot exceed 253 characters in length, if this length limit is enforced prior to passing the domain to the idna.encode() function it should no longer consume significant resources. This is triggered by arbitrarily large inputs that would not occur in normal usage, but may be passed to the library assuming there is no preliminary input validation by the higher-level application.
References
Impact
A specially crafted argument to the idna.encode() function could consume significant resources. This may lead to a denial-of-service.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2024-3651 has a CVSS score of 6.2 (Medium). The vector is requires local access, 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 (3.7); 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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The function has been refined to reject such strings without the associated resource consumption in version 3.7.
Frequently Asked Questions
- What is CVE-2024-3651? CVE-2024-3651 is a medium-severity uncontrolled resource consumption vulnerability in idna (pip), affecting versions < 3.7. It is fixed in 3.7. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2024-3651? CVE-2024-3651 has a CVSS score of 6.2 (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 idna are affected by CVE-2024-3651? idna (pip) versions < 3.7 is affected.
- Is there a fix for CVE-2024-3651? Yes. CVE-2024-3651 is fixed in 3.7. Upgrade to this version or later.
- Is CVE-2024-3651 exploitable, and should I be worried? Whether CVE-2024-3651 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-2024-3651 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-2024-3651? Upgrade
idnato 3.7 or later.