How severe is CVE-2019-5420?

CVE-2019-5420 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2019-5420 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 92% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-5420?

CVE-2019-5420 primarily affects Rubyonrails Rails. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-5420?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2019-5420 published?

CVE-2019-5420 was published on 2019-03-27 and last updated on 2026-06-17.

CVE-2019-5420

CVE-2019-5420 is a critical-severity vulnerability in Rubyonrails Rails with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 92% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-330.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 92% (100th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-330
Affected product: Rubyonrails Rails
Published: 2019-03-27
Last modified: 2026-06-17

Description

A remote code execution vulnerability in development mode Rails <5.2.2.1, <6.0.0.beta3 can allow an attacker to guess the automatically generated development mode secret token. This secret token can be used in combination with other Rails internals to escalate to a remote code execution exploit.

Frequently asked questions

What is CVE-2019-5420?: A remote code execution vulnerability in development mode Rails <5.2.2.1, <6.0.0.beta3 can allow an attacker to guess the automatically generated development mode secret token. This secret token can be used in combination with other Rails internals to escalate to a remote code execution exploit.
How severe is CVE-2019-5420?: CVE-2019-5420 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2019-5420 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 92% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-5420?: CVE-2019-5420 primarily affects Rubyonrails Rails. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-5420?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2019-5420 published?: CVE-2019-5420 was published on 2019-03-27 and last updated on 2026-06-17.

References

Affected products (5)

cpe:2.3:a:rubyonrails:rails:*:*:*:*:*:*:*:*
cpe:2.3:a:rubyonrails:rails:6.0.0:beta1:*:*:*:*:*:*
cpe:2.3:a:rubyonrails:rails:6.0.0:beta2:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*

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