← Vulnerability feed

Vulnerability record · CVE-2021-3450 · published 25 March 2021

CVE-2021-3450: Openssl improper certificate validation vulnerability

OOpenssl · Openssl

The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. If a "purpose" has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named "purpose" values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j).

7.4 CVSS 3.1 High EPSS 18% · top 2.9% CWE-295 · Improper certificate validation
7.4CVSS 3.1 base score, v2 5.8
18%EPSS exploitation probability, 30 days
NoNot in CISA KEV
33Affected product versions listed by NVD
48References
17 Jun 2026Last modified by NVD

Description

The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. If a "purpose" has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named "purpose" values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j).

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

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

References

LinkTags
http://www.openwall.com/lists/oss-security/2021/03/27/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/27/2 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/28/3 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/28/4 Mailing ListThird Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf Third Party Advisory
https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=2a40b7bc7b94dd7de897a74571e7024f0cf0d63b
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845 Third Party Advisory
https://kc.mcafee.com/corporate/index?page=content&id=SB10356 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBFLLVQVILIVGZMBJL3IXZ
https://mta.openssl.org/pipermail/openssl-announce/2021-March/000198.html Mailing ListVendor Advisory
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013 Third Party Advisory
https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.asc Third Party Advisory
https://security.gentoo.org/glsa/202103-03 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210326-0006/ Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-GHY28dJd Third Party Advisory
https://www.openssl.org/news/secadv/20210325.txt Vendor Advisory
https://www.oracle.com//security-alerts/cpujul2021.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuApr2021.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory
https://www.tenable.com/security/tns-2021-05 Third Party Advisory
https://www.tenable.com/security/tns-2021-08 Third Party Advisory
https://www.tenable.com/security/tns-2021-09 Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/27/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/27/2 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/28/3 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/03/28/4 Mailing ListThird Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf Third Party Advisory
https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=2a40b7bc7b94dd7de897a74571e7024f0cf0d63b
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845 Third Party Advisory
https://kc.mcafee.com/corporate/index?page=content&id=SB10356 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBFLLVQVILIVGZMBJL3IXZ
https://mta.openssl.org/pipermail/openssl-announce/2021-March/000198.html Mailing ListVendor Advisory
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013 Third Party Advisory
https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.asc Third Party Advisory
https://security.gentoo.org/glsa/202103-03 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210326-0006/ Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-GHY28dJd Third Party Advisory
https://www.openssl.org/news/secadv/20210325.txt Vendor Advisory

Track CVE-2021-3450 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

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

10.0CVE-2021-44228Apache Log4j2 JNDI lookup remote code executionApache Log4j2 versions 2.0-beta9 through 2.15.0 (excluding 2.12.2, 2.12.3, and 2.3.1) do not protect against attacker-controlled LDAP and other JNDI …KEVEPSS 100%analysed9.8CVE-2024-4577PHP-CGI on Windows argument injection leads to remote code executionPHP-CGI on Windows can misinterpret characters in the command line passed to Win32 API functions when certain code pages are configured, due to Windo…KEVEPSS 100%analysed9.8CVE-2021-44026Roundcube Webmail SQL injection via search parametersRoundcube Webmail before 1.3.17 and 1.4.x before 1.4.12 is prone to SQL injection through the search or search_params input. The flaw is remotely rea…KEVEPSS 70%analysed9.8CVE-2021-42013Apache HTTP Server path traversal and RCE via incomplete fixThe fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient, leaving a path traversal flaw that lets attackers map URLs to files outside…KEVEPSS 100%analysed9.8CVE-2021-41773Apache HTTP Server 2.4.49 path traversal and RCEA path normalization flaw introduced in Apache HTTP Server 2.4.49 lets attackers map URLs to files outside directories configured by Alias-like direc…KEVEPSS 100%analysed9.8CVE-2021-1870Apple WebKit logic flaw allows remote code executionA logic issue in Apple's WebKit was addressed with improved restrictions, affecting macOS Big Sur, Catalina, Mojave, iOS and iPadOS, plus WebKitGTK a…KEVEPSS 7.7%analysed9.8CVE-2021-1871Apple WebKit logic flaw allows remote code executionA logic issue in Apple's WebKit was addressed with improved restrictions. It affects macOS Big Sur, Catalina, Mojave, iOS and iPadOS, and a remote at…KEVEPSS 7.0%analysed9.8CVE-2020-16846SaltStack Salt API shell injection via crafted web requestsSaltStack Salt through 3002 is vulnerable to OS command injection when the SSH client is enabled and crafted web requests are sent to the Salt API. T…KEVEPSS 100%analysed

Source: NIST National Vulnerability Database (record CVE-2021-3450), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.