CVE-2026-45363
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedruby-jwt is a Ruby implementation of the RFC 7519 OAuth JSON Web Token standard. Prior to 2.10.3 and 3.2.0, JWT.decode(token, '', true, algorithm: 'HS256') accepts an attacker-forged token because OpenSSL::HMAC.digest('SHA256', '', payload) returns a valid digest under an empty key and no empty-key precondition exists in the HMAC algorithm. The same path is reached when a keyfinder block or key_finder: argument returns an empty string, nil, or an array containing nil for an unknown key, affecting HS256, HS384, and HS512 verification through JWT.decode and JWT::EncodedToken#verify_signature!. This issue is fixed in versions 2.10.3 and 3.2.0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceruby-jwt fails to validate keys in HMAC-based algorithms (HS256, HS384, HS512), allowing JWT.decode to accept attacker-forged tokens when an empty string, nil, or keyfinder-returned null is used as the secret key. OpenSSL::HMAC.digest produces valid signatures under empty keys without any precondition check.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify ruby-jwt versionRun `gem list ruby-jwt` or check the Gemfile.lock for the ruby-jwt gem versionAffected if The installed version is below 2.10.3 or 3.2.0 (or if no version is listed, the gem is present and HMAC algorithms are used)
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Locate JWT.decode callsSearch codebase for `JWT.decode` method calls, particularly focusing on calls using HS256, HS384, or HS512 algorithmsAffected if JWT.decode is called with HMAC-based algorithms without explicit key validation
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Inspect secret key usageReview all JWT.decode invocations and identify where the secret key argument comes from (hardcoded, environment variable, keyfinder block)Affected if The secret key is sourced from variables that could be empty string, nil, or undefined/null values
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Audit keyfinder implementationsSearch for keyfinder blocks passed to JWT.decode options (e.g., `key: ->` or `keyfinder:`) and examine what values they returnAffected if Any keyfinder lambda/proc can return nil, empty string, or no value at all
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Check for algorithm parameterExamine JWT.decode calls for the `algorithm` parameter - look specifically for HS256, HS384, or HS512Affected if HMAC algorithms are explicitly specified in JWT.decode calls and the key is not validated to be non-empty before use
You are affected if ruby-jwt is installed with HMAC algorithm usage and any JWT.decode call can receive an empty string, nil, or null-returning keyfinder as the secret key.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade ruby-jwt to version 2.10.3 or 3.2.0 or later. Audit all keyfinder implementations and JWT.decode calls to ensure non-empty keys are always provided.
ruby-jwt version 2.10.3 or 3.2.0 (whichever branch you are on)
- Identify the current ruby-jwt version in your Gemfile or Gemfile.lock (e.g., run `bundle show ruby-jwt` or check the installed version)
- If using version 2.x, upgrade to version 2.10.3 or later by running `bundle update ruby-jwt` or specifying `gem 'ruby-jwt', '~> 2.10.3'` in your Gemfile
- If using version 3.x, upgrade to version 3.2.0 or later by running `bundle update ruby-jwt` or specifying `gem 'ruby-jwt', '~> 3.2.0'` in your Gemfile
- Run `bundle install` or `bundle update` to install the updated gem
- Verify the upgrade was successful by checking the installed version: `bundle show ruby-jwt`
- Test your application to ensure token verification still functions correctly after the upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45363 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-45363 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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