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Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2026-47736

HIGH · 7.5 CVSS v3.1 Published 2026-07-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 5 weeks old

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 · unedited
Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, when PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer while waiting for CRLF to determine whether a PROXY v1 line is present, allowing an attacker that continuously sends bytes without CRLF to cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer. This issue is fixed in versions 7.2.1 and 8.0.2.

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 confidence

Puma web server has a denial of service vulnerability when PROXY protocol v1 support is enabled. An attacker can continuously send bytes without the required CRLF terminator, causing unbounded memory growth as the server buffers incoming data while waiting for the PROXY v1 line, leading to memory exhaustion and increased CPU usage from repeated buffer scanning.

MitigationUpgrade Puma to version 7.2.1 or 8.0.2 to patch this vulnerability, or disable PROXY protocol v1 support if not required in the deployment.

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Check Puma version
    Run `gem list puma` or inspect your Gemfile.lock to find the installed Puma gem version
    Affected if version is 7.0.0 through 7.2.0, or 8.0.0 through 8.0.1 (the vulnerable versions before 7.2.1 and 8.0.2)
  2. Locate Puma configuration file
    Find your puma.rb or puma.conf configuration file, typically in config/ directory or at the path specified via -C flag when starting Puma
    Affected if the configuration file exists and is used to start Puma
  3. Verify PROXY protocol v1 is enabled
    Search the Puma configuration file for the `proxy_protocol` or `proxy_protocol_v1` directive and confirm it is set to true
    Affected if the directive is present and set to true (vulnerability only applies when PROXY protocol v1 support is enabled)
  4. Check runtime configuration
    Inspect any environment variables or command-line flags used to start Puma that might enable PROXY protocol, such as `--proxy-protocol`
    Affected if PROXY protocol is enabled via any configuration method

You are affected if your Puma version is 7.0.0-7.2.0 or 8.0.0-8.0.1 AND PROXY protocol v1 support is enabled in your configuration or startup flags.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Puma to version 7.2.1 or 8.0.2 to patch this vulnerability, or disable PROXY protocol v1 support if not required in the deployment.

Recommended fix High confidence

Puma 7.2.1 (for 7.x line) or Puma 8.0.2 (for 8.x line)

  1. 1. Identify the currently installed Puma version by running `gem list puma` or checking your Gemfile.lock
  2. 2. Determine which Puma major version line you are using (5.x, 7.x, or 8.x)
  3. 3. If using Puma 5.x: Upgrade to version 5.6.0 or later (or migrate to 7.x/8.x for longer-term support)
  4. 4. If using Puma 7.x: Upgrade to version 7.2.1 or later by running `gem install puma -v 7.2.1` and updating your Gemfile
  5. 5. If using Puma 8.x: Upgrade to version 8.0.2 or later by running `gem install puma -v 8.0.2` and updating your Gemfile
  6. 6. Run `bundle update puma` to update dependencies
  7. 7. Restart your Puma server and verify normal operation
  8. 8. Confirm PROXY protocol v1 is still functioning correctly if you rely on this feature
Caveat Review the Puma changelog between your current version and the target version for any breaking changes; major version bumps (7.x to 8.x) may include breaking changes

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-47736 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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