CVE-2026-45363 is a high-severity improper authentication vulnerability in jwt (rubygems), affecting versions >= 3.0.0, < 3.2.0. It is fixed in 3.2.0, 2.10.3.
JWT.decode(token, '', true, algorithm: 'HS256') accepts an attacker-forged token. OpenSSL::HMAC.digest('SHA256', '', payload) returns a valid digest under an empty key, and no raise InvalidKeyError if key.empty? precondition exists in the HMAC algorithm. The same path is reached when a keyfinder block or keyfinder: argument returns "", nil, or an array containing nil for an unknown key. JWT::Decode#findkey only rejects literal nil and empty arrays, and JWT::JWA::Hmac silently coerces nil to "" (signingkey ||= '') before signing. Common application patterns that produce the unsafe value: redis.get("kid:#{kid}").tos, ORM string columns with default: '', ENV['SECRET'] || '', Hash.new('') lookups, [primary, fallback] where fallback may be nil. Applications passing a non-empty static key:, or whose keyfinder returns nil / raises on miss, are not affected. The existing enforcehmackeylength option would block this but defaults to false. On OpenSSL ≥ 3.5 the empty-key HMAC.digest call no longer raises, so the OpenSSL-3.0 rescue in JWA::Hmac#sign does not fire. Affects HS256/HS384/HS512 via both JWT.decode (positional key and block keyfinder) and JWT::EncodedToken#verifysignature!(key_finder:)
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2026-45363 has a CVSS score of 7.4 (High). 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 (3.2.0, 2.10.3). Upgrading removes the vulnerable code path.
rubygems
jwt (>= 3.0.0, < 3.2.0)jwt (< 2.10.3)jwt → 3.2.0 (rubygems)jwt → 2.10.3 (rubygems)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 instead of chasing every advisory.
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Upgrade the following packages to resolve this vulnerability:
jwt to 3.2.0 or laterjwt to 2.10.3 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-45363 is a high-severity improper authentication vulnerability in jwt (rubygems), affecting versions >= 3.0.0, < 3.2.0. It is fixed in 3.2.0, 2.10.3. The application does not adequately verify the identity of a user, device, or process before granting access.
CVE-2026-45363 has a CVSS score of 7.4 (High). 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.
jwt (rubygems) versions >= 3.0.0, < 3.2.0 is affected.
Yes. CVE-2026-45363 is fixed in 3.2.0, 2.10.3. Upgrade to this version or later.
Whether CVE-2026-45363 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
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.
jwt to 3.2.0 or laterjwt to 2.10.3 or later