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Vulnerability record · CVE-2016-3739 · published 20 May 2016

CVE-2016-3739: Haxx curl improper input validation vulnerability

Haxx · Curl

The (1) mbed_connect_step1 function in lib/vtls/mbedtls.c and (2) polarssl_connect_step1 function in lib/vtls/polarssl.c in cURL and libcurl before 7.49.0, when using SSLv3 or making a TLS connection to a URL that uses a numerical IP address, allow remote attackers to spoof servers via an arbitrary valid certificate.

5.3 CVSS 3.0 Medium EPSS 6.9% · top 6.1% CWE-20 · Improper input validation
5.3CVSS 3.0 base score, v2 2.6
6.9%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
22References
17 Jun 2026Last modified by NVD

Description

The (1) mbed_connect_step1 function in lib/vtls/mbedtls.c and (2) polarssl_connect_step1 function in lib/vtls/polarssl.c in cURL and libcurl before 7.49.0, when using SSLv3 or making a TLS connection to a URL that uses a numerical IP address, allow remote attackers to spoof servers via an arbitrary valid certificate.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.openwall.com/lists/oss-security/2024/03/27/4
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.securityfocus.com/bid/90726
http://www.securitytracker.com/id/1035907
http://www.slackware.com/security/viewer.php?l=slackware-security&y=2016&m=slackware-security.495349
https://curl.haxx.se/CVE-2016-3739.patch Vendor Advisory
https://curl.haxx.se/changes.html#7_49_0
https://curl.haxx.se/docs/adv_20160518.html Vendor Advisory
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05320149
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722
https://security.gentoo.org/glsa/201701-47
http://www.openwall.com/lists/oss-security/2024/03/27/4
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.securityfocus.com/bid/90726
http://www.securitytracker.com/id/1035907
http://www.slackware.com/security/viewer.php?l=slackware-security&y=2016&m=slackware-security.495349
https://curl.haxx.se/CVE-2016-3739.patch Vendor Advisory
https://curl.haxx.se/changes.html#7_49_0
https://curl.haxx.se/docs/adv_20160518.html Vendor Advisory
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05320149
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722
https://security.gentoo.org/glsa/201701-47

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2016-3739), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.