PumaApplication
CVE-2024-45614
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 · uneditedPuma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.
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 confidencePuma web server fails to differentiate between proxy-set headers (X-Forwarded-For) and client-supplied underscore variants (X-Forwarded_For), allowing attackers to override or spoof values intended to be set by trusted reverse proxies. This header injection can affect security decisions based on those headers.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
PumaApplication
< 5.6.9>= 6.0.0, < 6.4.3CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/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 installed Puma versionRun `gem list puma` or check your Gemfile.lock for the puma gem version, or run `puma --version` if CLI availableAffected if The version is below 5.6.9, or between 6.0.0 and 6.4.3 (inclusive)
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Determine if Puma is exposed directly to clientsCheck your server deployment architecture: is Puma listening directly on a public IP/port, or is there a reverse proxy (Nginx, Apache, load balancer) in front of it? Review your deploy configuration or run `netstat -tlnp | grep puma` to see listening addressesAffected if Puma is directly accessible to untrusted clients without an intervening reverse proxy
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Check reverse proxy configuration for underscore handlingIf a reverse proxy exists, examine its configuration for the `underscores_in_headers` directive (Nginx: `underscores_in_headers on/off`; Apache: `RegexRequestUri` patterns). Look for any settings that allow underscore-prefixed headers to pass through to PumaAffected if The proxy is configured to allow (or does not explicitly block) headers with underscores, or no proxy exists between clients and Puma
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Verify X-Forwarded_For header processingSend a test request with both `X-Forwarded-For` and `X-Forwarded_For` headers (note the underscore vs hyphen) to your Puma endpoint using curl or similar: `curl -H 'X-Forwarded-For: 1.2.3.4' -H 'X-Forwarded_For: 5.6.7.8' http://your-server/` and inspect which value Puma/app reportsAffected if The underscore variant (X-Forwarded_For) takes precedence or is processed identically to the hyphenated version, indicating Puma is treating them as equivalent
You are affected if your Puma version is < 5.6.9 or >= 6.0.0 and < 6.4.3 AND clients can directly send requests to Puma or your reverse proxy passes underscore-prefixed headers through to Puma.
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 · scoped5.6.96.4.3
Upgrade Puma to v6.4.3 or v5.6.9, or configure upstream proxies (e.g., Nginx) with underscores_in_headers off to discard underscore-prefixed headers before they reach the application.
Puma 6.4.3 (for 6.x users) or Puma 5.6.9 (for 5.x users)
- Identify the currently installed Puma version by checking your Gemfile, Gemfile.lock, or running `puma --version`
- If using Puma 6.x, upgrade to version 6.4.3 or later
- If using Puma 5.x, upgrade to version 5.6.9 or later
- Update your Gemfile with the appropriate version constraint (e.g., gem 'puma', '~> 6.4' or gem 'puma', '~> 5.6')
- Run `bundle update puma` to install the fixed version
- Restart your application to load the new Puma version
- Optional nginx mitigation: Add or set `underscores_in_headers off;` in your nginx.conf server/location block to discard headers with underscores at the proxy level
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Puma
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2024-45614 — 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-2024-45614 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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