How severe is CVE-2016-5420?

CVE-2016-5420 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2016-5420 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-5420?

CVE-2016-5420 primarily affects Haxx Libcurl. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-5420?

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

When was CVE-2016-5420 published?

CVE-2016-5420 was published on 2016-08-10 and last updated on 2026-06-17.

CVE-2016-5420

CVE-2016-5420 is a high-severity vulnerability in Haxx Libcurl with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 15% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-285.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 15% (96th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-285
Affected product: Haxx Libcurl
Published: 2016-08-10
Last modified: 2026-06-17

Description

curl and libcurl before 7.50.1 do not check the client certificate when choosing the TLS connection to reuse, which might allow remote attackers to hijack the authentication of the connection by leveraging a previously created connection with a different client certificate.

Frequently asked questions

What is CVE-2016-5420?: curl and libcurl before 7.50.1 do not check the client certificate when choosing the TLS connection to reuse, which might allow remote attackers to hijack the authentication of the connection by leveraging a previously created connection with a different client certificate.
How severe is CVE-2016-5420?: CVE-2016-5420 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2016-5420 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-5420?: CVE-2016-5420 primarily affects Haxx Libcurl. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-5420?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2016-5420 published?: CVE-2016-5420 was published on 2016-08-10 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:a:haxx:libcurl:*:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*

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