How severe is CVE-2015-4020?

CVE-2015-4020 has a CVSS 2.0 base score of 4.3, rated medium severity.

Is CVE-2015-4020 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2015-4020?

CVE-2015-4020 primarily affects Rubygems. In total, 36 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2015-4020?

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

When was CVE-2015-4020 published?

CVE-2015-4020 was published on 2015-08-25 and last updated on 2026-06-17.

CVE-2015-4020

CVE-2015-4020 is a medium-severity vulnerability in Rubygems with a CVSS 2.0 base score of 4.3. 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-20.

Key facts

Severity: Medium (CVSS 2.0 base score 4.3)
EPSS exploit prediction: 3% (88th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Rubygems
Published: 2015-08-25
Last modified: 2026-06-17

Description

RubyGems 2.0.x before 2.0.17, 2.2.x before 2.2.5, and 2.4.x before 2.4.8 does not validate the hostname when fetching gems or making API requests, which allows remote attackers to redirect requests to arbitrary domains via a crafted DNS SRV record with a domain that is suffixed with the original domain name, aka a "DNS hijack attack." NOTE: this vulnerability exists because to an incomplete fix for CVE-2015-3900.

Frequently asked questions

What is CVE-2015-4020?: RubyGems 2.0.x before 2.0.17, 2.2.x before 2.2.5, and 2.4.x before 2.4.8 does not validate the hostname when fetching gems or making API requests, which allows remote attackers to redirect requests to arbitrary domains via a crafted DNS SRV record with a domain that is suffixed with the original domain name, aka a "DNS hijack attack." NOTE: this vulnerability exists because to an incomplete fix for CVE-2015-3900.
How severe is CVE-2015-4020?: CVE-2015-4020 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2015-4020 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2015-4020?: CVE-2015-4020 primarily affects Rubygems. In total, 36 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2015-4020?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2015-4020 published?: CVE-2015-4020 was published on 2015-08-25 and last updated on 2026-06-17.

References

Affected products (36)

cpe:2.3:o:oracle:solaris:11.3:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:preview2:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:preview2.1:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:preview2.2:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:rc1:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.0:rc2:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.1:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.2:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.3:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.4:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.5:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.6:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.7:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.8:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.9:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.10:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.11:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.12:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.13:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.14:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.15:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.0.16:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.2.0:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.2.1:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.2.2:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.2.3:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.2.4:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.0:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.1:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.2:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.3:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.4:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.5:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.6:*:*:*:*:*:*:*
cpe:2.3:a:rubygems:rubygems:2.4.7:*:*:*:*:*:*:*

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