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MEDIUM severity

GHSA-7xx3-m584-x994

MEDIUM

GHSA-7xx3-m584-x994 is a medium-severity (CVSS 5.3) CWE-770 vulnerability in puma. O3 Security confirms whether GHSA-7xx3-m584-x994 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

A poorly-behaved client could use keepalive requests to monopolize Puma's reactor and create a denial of service attack

Also known asCVE-2019-16770
Published
Dec 5, 2019
Updated
Jul 8, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Jul 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected
💎puma💎puma

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Keepalive thread overload/DoS

Impact

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.

Patches

This vulnerability is patched in Puma 4.3.1 and 3.12.2.

Workarounds

Reverse proxies in front of Puma could be configured to always allow less than X keepalive connections to a Puma cluster or process, where X is the number of threads configured in Puma's thread pool.

For more information

If you have any questions or comments about this advisory:

  • Open an issue at puma.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemspumaall versions3.12.2
💎RubyGemspuma4.0.0&&< 4.3.14.3.1

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for puma. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update puma to 3.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7xx3-m584-x994 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-7xx3-m584-x994 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-7xx3-m584-x994. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Keepalive thread overload/DoS ### Impact 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. ### Patches This vulnerability is patched in Puma 4.3.1 and 3.12.2. ### Workarounds Reverse proxies in front of Puma could be configured to always allow less than X keepalive connections to a Puma cluster or process, where X is the number of threads
O3 Security · Impact-Aware SCA

Is GHSA-7xx3-m584-x994 in your dependencies?

O3 detects GHSA-7xx3-m584-x994 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

GHSA-7xx3-m584-x994: puma Denial of… | O3 Security