How severe is CVE-2013-4366?

CVE-2013-4366 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-2013-4366 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2013-4366?

CVE-2013-4366 primarily affects Apache Httpclient. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2013-4366?

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-2013-4366 published?

CVE-2013-4366 was published on 2017-10-30 and last updated on 2026-06-16.

CVE-2013-4366

CVE-2013-4366 is a critical-severity vulnerability in Apache Httpclient with a CVSS 3.x base score of 9.8. 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: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Apache Httpclient
Published: 2017-10-30
Last modified: 2026-06-16

Description

http/impl/client/HttpClientBuilder.java in Apache HttpClient 4.3.x before 4.3.1 does not ensure that X509HostnameVerifier is not null, which allows attackers to have unspecified impact via vectors involving hostname verification.

Frequently asked questions

What is CVE-2013-4366?: http/impl/client/HttpClientBuilder.java in Apache HttpClient 4.3.x before 4.3.1 does not ensure that X509HostnameVerifier is not null, which allows attackers to have unspecified impact via vectors involving hostname verification.
How severe is CVE-2013-4366?: CVE-2013-4366 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-2013-4366 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2013-4366?: CVE-2013-4366 primarily affects Apache Httpclient. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2013-4366?: 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-2013-4366 published?: CVE-2013-4366 was published on 2017-10-30 and last updated on 2026-06-16.

References

Affected products (4)

cpe:2.3:a:apache:httpclient:4.3:*:*:*:*:*:*:*
cpe:2.3:a:apache:httpclient:4.3:alpha1:*:*:*:*:*:*
cpe:2.3:a:apache:httpclient:4.3:beta1:*:*:*:*:*:*
cpe:2.3:a:apache:httpclient:4.3:beta2:*:*:*:*:*:*

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