Summary
Signature Verification Bypass in jwt-simple
Versions of jwt-simple prior to 0.5.3 are vulnerable to Signature Verification Bypass. If no algorithm is specified in the decode() function, the packages uses the algorithm in the JWT to decode tokens. This allows an attacker to create a HS256 (symmetric algorithm) JWT with the server's public key as secret, and the package will verify it as HS256 instead of RS256 (asymmetric algorithm).
Impact
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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Upgrade to version 0.5.3 or later.
Frequently Asked Questions
- What is GHSA-8V5F-HP78-JGXQ? GHSA-8V5F-HP78-JGXQ is a high-severity security vulnerability in jwt-simple (npm), affecting versions < 0.5.3. It is fixed in 0.5.3.
- Which versions of jwt-simple are affected by GHSA-8V5F-HP78-JGXQ? jwt-simple (npm) versions < 0.5.3 is affected.
- Is there a fix for GHSA-8V5F-HP78-JGXQ? Yes. GHSA-8V5F-HP78-JGXQ is fixed in 0.5.3. Upgrade to this version or later.
- Is GHSA-8V5F-HP78-JGXQ exploitable, and should I be worried? Whether GHSA-8V5F-HP78-JGXQ 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 GHSA-8V5F-HP78-JGXQ 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 GHSA-8V5F-HP78-JGXQ? Upgrade
jwt-simpleto 0.5.3 or later.