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Fencer Intel
high 7.5

CVE-2016-5420 in the critical feed json

curl and libcurl before 7.50.1 do not check the client certificate when choosing the TLS connection to reuse, which might allow remote atta…

published 2016-08-10 10 y ago modified 2026-06-17 4 mo ago also EUVD-2016-6365

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
15.4%
EPSS 15.4% chance of exploitation in 30 days, percentile 96%
public exploits
0
none known

Summary

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.

Patch / fix

  • curl Debian 14, Debian 13, Debian 12 7.50.1-1

debian advisories DEBIAN-CVE-2016-5420

  • curl Ubuntu 14.04 LTS 7.35.0-1ubuntu2.8
  • curl Ubuntu 16.04 LTS 7.47.0-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2016-5420

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • httpd24-curl RHEL 3 SOFTWARE_COLLECTIONS 7.61.1-1.el6
  • httpd24-curl RHEL 3 SOFTWARE_COLLECTIONS 7.61.1-1.el7
  • httpd24-httpd RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-7.el6
  • httpd24-httpd RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-7.el7
  • httpd24-mod_md RHEL 3 SOFTWARE_COLLECTIONS 2.4.34-7.el7
  • httpd24-libcurl RHEL 3 SOFTWARE_COLLECTIONS 7.61.1-1.el6
  • httpd24-libcurl RHEL 3 SOFTWARE_COLLECTIONS 7.61.1-1.el7
  • httpd24-mod_ssl RHEL 3 SOFTWARE_COLLECTIONS 1:2.4.34-7.el6

red hat advisories RHSA-2018:3558RHSA-2016:2575

  • curl Studio Onsite 1.3 7.19.7-1.20.47.2
  • curl SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +6 more 7.19.7-1.61.1
  • curl-openssl1 SLES 11-SECURITY, SLES 11 SP3-TERADATA, SLES 11 SP3-LTSS 7.19.7-1.61.1
  • curl SLES for SAP 12 SP1, SLES 12 SP1, SLED 12 SP1 +1 more 7.37.0-28.1
  • curl Studio Onsite 1.3 7.19.7-1.20.42.1

suse advisories SUSE-SU-2016:2700-1SUSE-SU-2016:2449-1SUSE-SU-2016:2330-1SUSE-SU-2016:2155-1

  • curl Alpine 3.24, Alpine 3.23, Alpine 3.22 +14 more 7.50.1-r0
  • curl Alpine 3.11, Alpine 3.8, Alpine 3.7 +1 more 7.50.1
  • curl Alpine 3.3, Alpine 3.2 7.49.1-r1

alpine advisories ALPINE-CVE-2016-5420

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-5420 updated cvss 4.2

curl: Re-using connection with wrong client cert

  • Red Hat .NET Core 1.0 on Red Hat Enterprise Linux rh-dotnetcore10-curl Red Hat .NET Core 1.1 on Red Hat Enterprise Linux rh-dotnetcore11-curl Red Hat .NET Core 2.0 on Red Hat Enterprise Linux rh-dotnet20-curl
    affected: no fix planned “Out of support scope”
  • Red Hat .NET Core 2.1 on Red Hat Enterprise Linux rh-dotnet21-curl, rh-dotnet21-libcurl Red Hat Enterprise Linux 5 curl Red Hat Enterprise Linux 6 curl, libcurl Red Hat Enterprise Virtualization 3 mingw-virt-viewer, mingw32-virt-viewer, mingw64-virt-viewer
    affected: no fix planned “Will not fix”
  • Red Hat JBoss Enterprise Web Server 3 curl
    affected: no fix available
  • Red Hat Enterprise Linux Client (v. 7) curl 7.29.0-35.el7, libcurl 7.29.0-35.el7 Red Hat Enterprise Linux Client Optional (v. 7) libcurl-devel 7.29.0-35.el7, curl-debuginfo 7.29.0-35.el7 Red Hat Enterprise Linux ComputeNode (v. 7) curl 7.29.0-35.el7, libcurl 7.29.0-35.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) libcurl-devel 7.29.0-35.el7, curl-debuginfo 7.29.0-35.el7 Red Hat Enterprise Linux Server (v. 7) curl 7.29.0-35.el7, libcurl 7.29.0-35.el7 Red Hat Enterprise Linux Workstation (v. 7) curl 7.29.0-35.el7, libcurl 7.29.0-35.el7
    fixed: vendor fix RHSA-2016:2575
  • Red Hat JBoss Core Services
    fixed: vendor fix RHSA-2016:2957
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) httpd24-curl 7.61.1-1.el6, httpd24-httpd 2.4.34-7.el6, httpd24-nghttp2 1.7.1-7.el6, httpd24-libcurl 7.61.1-1.el6, httpd24-mod_ssl 2.4.34-7.el6, httpd24-mod_ldap 2.4.34-7.el6, +5 more Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) httpd24-curl 7.61.1-1.el7, httpd24-httpd 2.4.34-7.el7, httpd24-mod_md 2.4.34-7.el7, httpd24-nghttp2 1.7.1-7.el7, httpd24-libcurl 7.61.1-1.el7, httpd24-mod_ssl 2.4.34-7.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.4) httpd24-curl 7.61.1-1.el7, httpd24-httpd 2.4.34-7.el7, httpd24-mod_md 2.4.34-7.el7, httpd24-nghttp2 1.7.1-7.el7, httpd24-libcurl 7.61.1-1.el7, httpd24-mod_ssl 2.4.34-7.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.5) httpd24-curl 7.61.1-1.el7, httpd24-httpd 2.4.34-7.el7, httpd24-mod_md 2.4.34-7.el7, httpd24-nghttp2 1.7.1-7.el7, httpd24-libcurl 7.61.1-1.el7, httpd24-mod_ssl 2.4.34-7.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.6) httpd24-curl 7.61.1-1.el7, httpd24-httpd 2.4.34-7.el7, httpd24-mod_md 2.4.34-7.el7, httpd24-nghttp2 1.7.1-7.el7, httpd24-libcurl 7.61.1-1.el7, httpd24-mod_ssl 2.4.34-7.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) httpd24-curl 7.61.1-1.el6, httpd24-httpd 2.4.34-7.el6, httpd24-nghttp2 1.7.1-7.el6, httpd24-libcurl 7.61.1-1.el6, httpd24-mod_ssl 2.4.34-7.el6, httpd24-mod_ldap 2.4.34-7.el6, +5 more
    +1 more products
    Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) httpd24-curl 7.61.1-1.el7, httpd24-httpd 2.4.34-7.el7, httpd24-mod_md 2.4.34-7.el7, httpd24-nghttp2 1.7.1-7.el7, httpd24-libcurl 7.61.1-1.el7, httpd24-mod_ssl 2.4.34-7.el7, +6 more
    fixed: vendor fix RHSA-2018:3558

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

15.36% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.