PumaApplication
CVE-2019-16770
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 · uneditedIn Puma before versions 3.12.2 and 4.3.1, a poorly-behaved client could use keepalive requests to monopolize Puma's reactor and create a denial of service attack. If more keepalive connections to Puma are opened than there are threads available, additional connections will wait permanently if the attacker sends requests frequently enough. This vulnerability is patched in Puma 4.3.1 and 3.12.2.
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 confidenceIn Puma web server before versions 3.12.2 and 4.3.1, a keepalive request handling vulnerability allows a poorly-behaved client to monopolize the server's reactor thread pool. By opening more keepalive connections than available threads and sending requests frequently, an attacker can cause legitimate connections to wait permanently, resulting in denial of service.
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
>= 3.0.0, < 3.12.2>= 4.0.0, < 4.3.1
Debian LinuxOperating system
= 9.0CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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 Puma installationRun `gem list puma` or check your Gemfile.lock for a puma entry, or look for puma in your package manager (dpkg -l | grep puma for Debian)Affected if puma is present in the gem or package listing
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Check Puma versionRun `puma -V` or `gem list puma --remote` and compare the version number against the affected ranges (3.0.0 to 3.12.1, or 4.0.0 to 4.3.0)Affected if the installed version falls within 3.0.0 to 3.12.1 or 4.0.0 to 4.3.0
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Verify Debian-packaged Puma version (if using system packages)Run `dpkg -l | grep -i puma` to list the installed puma package and its versionAffected if the Debian package version is between 3.0.0 and 3.12.1 or between 4.0.0 and 4.3.0
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Confirm network exposure (required for exploitation)Check your Puma configuration for bound addresses (default is 0.0.0.0:9292 or similar) and verify whether the port is accessible from untrusted networks using netstat or ssAffected if Puma is bound to a publicly accessible network interface with no firewall or rate limiting in front of it
You are affected if you are running any Puma version from 3.0.0 to 3.12.1 or 4.0.0 to 4.3.0 that is network-accessible, since the keepalive vulnerability can be exploited remotely to cause denial of service.
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.
From vendor data3.12.24.3.1
Upgrade Puma to version 3.12.2 or 4.3.1 or later to patch the reactor monopolization vulnerability. Consider implementing connection rate limiting as an additional defense-in-depth measure.
Fix this in Puma
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 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 $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-16770 — 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-2019-16770 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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