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No exploitation reportedFix available

CVE-2019-16770

No exploitation reported by the sources we read.

  • Published2019-12-05
  • Fixed in4.3.1 · 3.12.2
  • WeaknessCWE-770

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In 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.

Timeline

dates in UTC
  1. 2019-12-0520:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2019-16770?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2019-16770?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Puma
BranchAffectedFixed in
4.x≥ 4.0.0, < 4.3.14.3.1
3.x≥ 3.0.0, < 3.12.23.12.2
3.12< 3.12.23.12.2
Debian debian linux
BranchAffectedFixed in
9.0= 9.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Puma to 4.3.1 · 3.12.2

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CNACVSS 3.15.3read 2026-10-23
  • NVDCVSS 3.17.5read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • CNAweakness (CWE)CWE-770read 2026-10-23
  • NVDweakness (CWE)CWE-770read 2026-10-23
  • FIRST EPSSEPSS score2.0 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2019-12-05
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2019-16770?

In 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.

Is CVE-2019-16770 actively exploited?

Active exploitation of CVE-2019-16770 has not been confirmed. Its EPSS score was 2.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-16770?

CVE-2019-16770 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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