CVE-2021-3449

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions 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 1.1.1-1.1.1j).

• CWE-476

• http://www.openwall.com/lists/oss-security/2021/03/27/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/27/2Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/28/3Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/28/4Mailing List, Third Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfThird Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-772220.pdfPatch, Third Party Advisory
• https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb9fa6b51defd48157eeb207f52181f735d96148
• https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845Third Party Advisory
• https://kc.mcafee.com/corporate/index?page=content&id=SB10356Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/08/msg00029.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBFLLVQVILIVGZMBJL3IXZGKWQISYNP/
• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013Third Party Advisory
• https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.ascThird Party Advisory
• https://security.gentoo.org/glsa/202103-03Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210326-0006/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210513-0002/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20240621-0006/
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-GHY28dJdThird Party Advisory
• https://www.debian.org/security/2021/dsa-4875Third Party Advisory
• https://www.openssl.org/news/secadv/20210325.txtVendor Advisory
• https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuApr2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpujul2022.htmlThird Party Advisory
• https://www.oracle.com/security-alerts/cpuoct2021.htmlThird Party Advisory
• https://www.tenable.com/security/tns-2021-05Third Party Advisory
• https://www.tenable.com/security/tns-2021-06Third Party Advisory
• https://www.tenable.com/security/tns-2021-09Third Party Advisory
• https://www.tenable.com/security/tns-2021-10Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/27/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/27/2Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/28/3Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/03/28/4Mailing List, Third Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfThird Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-772220.pdfPatch, Third Party Advisory
• https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb9fa6b51defd48157eeb207f52181f735d96148
• https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845Third Party Advisory
• https://kc.mcafee.com/corporate/index?page=content&id=SB10356Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/08/msg00029.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBFLLVQVILIVGZMBJL3IXZGKWQISYNP/
• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013Third Party Advisory
• https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.ascThird Party Advisory
• https://security.gentoo.org/glsa/202103-03Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210326-0006/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210513-0002/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20240621-0006/
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-GHY28dJdThird Party Advisory
• https://www.debian.org/security/2021/dsa-4875Third Party Advisory
• https://www.openssl.org/news/secadv/20210325.txtVendor Advisory
• https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuApr2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpujul2022.htmlThird Party Advisory
• https://www.oracle.com/security-alerts/cpuoct2021.htmlThird Party Advisory
• https://www.tenable.com/security/tns-2021-05Third Party Advisory
• https://www.tenable.com/security/tns-2021-06Third Party Advisory
• https://www.tenable.com/security/tns-2021-09Third Party Advisory
• https://www.tenable.com/security/tns-2021-10Third Party Advisory

Published

Mar 25, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
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