CVE-2016-5420

HIGHEPSS 96th pctl

7.5

CVSS v3

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.

CWE-285

How to fix

Remediation Available

curlDebian

Fixed in:7.50.1-1CVE-2016-5420

curlUbuntu

Fixed in:7.35.0-1ubuntu2.8USN-3048-1

Fixed in:7.47.0-1ubuntu2.1USN-3048-1

libcurl3Ubuntu

Fixed in:7.35.0-1ubuntu2.8USN-3048-1

Fixed in:7.47.0-1ubuntu2.1USN-3048-1

libcurl3-gnutlsUbuntu

Fixed in:7.35.0-1ubuntu2.8USN-3048-1

Fixed in:7.47.0-1ubuntu2.1USN-3048-1

libcurl3-nssUbuntu

Fixed in:7.35.0-1ubuntu2.8USN-3048-1

Fixed in:7.47.0-1ubuntu2.1USN-3048-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Exploit Intelligence

14.60%probability of exploitation in 30 days

96thpercentile

Very high risk: more likely to be exploited than 96% of all known CVEs.

References

Patch1

curl.haxx.se

Third-Party Advisory2

Other references15

Related Vulnerabilities

Other CWE-285 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-29927	Critical	9.1	99%	-	Fix
CVE-2023-32707	High	8.8	79%	-	Fix
CVE-2021-28799	Critical	10.0	78%	KEV + Ransom	Fix
CVE-2023-48241	High	7.5	73%	-	Fix
CVE-2023-22480	High	7.3	67%	-	Fix
CVE-2022-3229	Critical	9.8	66%	-	-

Common questions

How do I fix CVE-2016-5420?

Published advisories record a fix for 5 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2016-5420 being actively exploited?

Not that we know of. CVE-2016-5420 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 14.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 96% of all scored CVEs.

How severe is CVE-2016-5420?

CVE-2016-5420 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2016-5420 affect?

Published advisories record a fix for curl (Debian), curl (Ubuntu), libcurl3 (Ubuntu), libcurl3-gnutls (Ubuntu), and 1 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-06.