--- title: "CVE-2021-3449: NULL pointer deref in signature_algorithms… | CubePath" description: "An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello…" language: en source: https://cubepath.com/security/cve/CVE-2021-3449 --- # CVE-2021-3449: NULL pointer deref in signature_algorithms… | CubePath ## Description 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). Official description from the CVE record, published by openssl. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-3449) ## Key data ### EPSS Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days. Score 0.63542 (63.5% probability) Percentile 99.2% Scores of Nov 10, 2026 Model v2026.06.15 ### CISA assessment as of Oct 8, 2026 Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA. Automatable yes Technical impact partial ## Affected products Products listed in the CVE record, as the CNA published them. - OpenSSL - affected: Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j) ## References Links listed in the CVE record. They lead to other sites, which CubePath does not control. - [openssl.org/news/secadv/20210325.txt](https://www.openssl.org/news/secadv/20210325.txt) - [git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb…](https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb9fa6b51defd48157eeb207f52181f735d96148) - [20210325 Multiple Vulnerabilities in OpenSSL Affecting Cisco Products: March 2021](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssl-2021-GHY28dJd) (tools.cisco.com) vendor-advisory - [DSA-4875](https://www.debian.org/security/2021/dsa-4875) (debian.org) vendor-advisory - [\[oss-security\] 20210327 OpenSSL 1.1.1 CVE-2021-3450 CA certificate check bypass with X509\_V\_FLAG\_X509\_STRICT, CVE-2021-3449 NULL pointer deref in signature\_algorithms processing](http://www.openwall.com/lists/oss-security/2021/03/27/1) (openwall.com) mailing-list - [\[oss-security\] 20210327 Re: OpenSSL 1.1.1 CVE-2021-3450 CA certificate check bypass with X509\_V\_FLAG\_X509\_STRICT, CVE-2021-3449 NULL pointer deref in signature\_algorithms processing](http://www.openwall.com/lists/oss-security/2021/03/27/2) (openwall.com) mailing-list - [\[oss-security\] 20210328 Re: OpenSSL 1.1.1 CVE-2021-3450 CA certificate check bypass with X509\_V\_FLAG\_X509\_STRICT, CVE-2021-3449 NULL pointer deref in signature\_algorithms processing](http://www.openwall.com/lists/oss-security/2021/03/28/3) (openwall.com) mailing-list - [\[oss-security\] 20210328 Re: OpenSSL 1.1.1 CVE-2021-3450 CA certificate check bypass with X509\_V\_FLAG\_X509\_STRICT, CVE-2021-3449 NULL pointer deref in signature\_algorithms processing](http://www.openwall.com/lists/oss-security/2021/03/28/4) (openwall.com) mailing-list - [GLSA-202103-03](https://security.gentoo.org/glsa/202103-03) (security.gentoo.org) vendor-advisory - [FEDORA-2021-cbf14ab8f9](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CCBFLLVQVILIVGZMBJL3IXZGKWQISYNP/) (lists.fedoraproject.org) vendor-advisory - [oracle.com/security-alerts/cpuApr2021.html](https://www.oracle.com/security-alerts/cpuApr2021.html) - [tenable.com/security/tns-2021-10](https://www.tenable.com/security/tns-2021-10) - [tenable.com/security/tns-2021-09](https://www.tenable.com/security/tns-2021-09) - [security.netapp.com/advisory/ntap-20210513-0002](https://security.netapp.com/advisory/ntap-20210513-0002/) - [security.netapp.com/advisory/ntap-20210326-0006](https://security.netapp.com/advisory/ntap-20210326-0006/) - [security.freebsd.org/advisories/FreeBSD-SA-21:07.openssl.asc](https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.asc) - [tenable.com/security/tns-2021-06](https://www.tenable.com/security/tns-2021-06) - [tenable.com/security/tns-2021-05](https://www.tenable.com/security/tns-2021-05) - [kc.mcafee.com/corporate/index?page=content&id=SB10356](https://kc.mcafee.com/corporate/index?page=content&id=SB10356) - [oracle.com//security-alerts/cpujul2021.html](https://www.oracle.com//security-alerts/cpujul2021.html) - [cert-portal.siemens.com/productcert/pdf/ssa-772220.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-772220.pdf) - [kb.pulsesecure.net/articles/Pulse\_Security\_Advisories/SA448…](https://kb.pulsesecure.net/articles/Pulse%5FSecurity%5FAdvisories/SA44845) - [psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013](https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013) - [\[debian-lts-announce\] 20210831 \[SECURITY\] \[DLA 2751-1\] postgresql-9.6 security update](https://lists.debian.org/debian-lts-announce/2021/08/msg00029.html) (lists.debian.org) mailing-list - [oracle.com/security-alerts/cpuoct2021.html](https://www.oracle.com/security-alerts/cpuoct2021.html) - [oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html) - [cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf) - [oracle.com/security-alerts/cpujul2022.html](https://www.oracle.com/security-alerts/cpujul2022.html) - [security.netapp.com/advisory/ntap-20240621-0006](https://security.netapp.com/advisory/ntap-20240621-0006/) ## Timeline 1. ID reserved Mar 17, 2021 2. Record published Mar 25, 2021 3. Record last updated Oct 8, 2026 ## Look up another CVE ## About CubePath CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection. [Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection) Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:02 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)