How severe is CVE-2019-16770?

CVE-2019-16770 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2019-16770 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-16770?

CVE-2019-16770 primarily affects Puma. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-16770?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-16770 published?

CVE-2019-16770 was published on 2019-12-05 and last updated on 2026-06-17.

CVE-2019-16770

CVE-2019-16770 is a medium-severity vulnerability in Puma with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Affected product: Puma
Published: 2019-12-05
Last modified: 2026-06-17

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.

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.
How severe is CVE-2019-16770?: CVE-2019-16770 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2019-16770 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-16770?: CVE-2019-16770 primarily affects Puma. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-16770?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-16770 published?: CVE-2019-16770 was published on 2019-12-05 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:puma:puma:*:*:*:*:*:ruby:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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