Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-3449

CVE-2021-3449MEDIUM

OpenSSL OpenSSL — NULL pointer deref in signature_algorithms processing

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   H   N   N  U  N  N  H    5.9   .6354   99.2     —

AFFECTED
  Product  Versions                                           Fixed
  OpenSSL  Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j) –  —

TIMELINE
  Mar 17  Reserved by openssl
  Mar 25  Published (CNA: openssl)
  Oct 8   ENRICHED — CVE-2021-3449 (OpenSSL). Received CVSS 5.9 and CPE data from NVD.

CWE-476 · CNA: openssl · CVSS v3.1 · 29 references · NVD status: Modified

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).

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
March 17, 2021	Reserved	Reserved by openssl
March 25, 2021	Published	Published (CNA: openssl)
October 8, 2026	ENRICHED	ENRICHED — CVE-2021-3449 (OpenSSL). Received CVSS 5.9 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
OpenSSL	OpenSSL	—	Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j)	—

Weaknesses

CWE-476

References (29)

http://www.openwall.com/lists/oss-security/2021/03/27/1 [Mailing List, Third Party Advisory]
http://www.openwall.com/lists/oss-security/2021/03/27/2 [Mailing List, Third Party Advisory]
http://www.openwall.com/lists/oss-security/2021/03/28/3 [Mailing List, Third Party Advisory]
http://www.openwall.com/lists/oss-security/2021/03/28/4 [Mailing List, Third Party Advisory]
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf [Third Party Advisory]
https://cert-portal.siemens.com/productcert/pdf/ssa-772220.pdf [Patch, Third Party Advisory]
https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb9fa6b51defd48157eeb207f52181f735d96148
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.debian.org/debian-lts-announce/2021/08/msg00029.html [Mailing 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-2021-0013 [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://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-GHY28dJd [Third Party Advisory]
https://www.debian.org/security/2021/dsa-4875 [Third Party Advisory]
https://www.openssl.org/news/secadv/20210325.txt [Vendor Advisory]
https://www.oracle.com//security-alerts/cpujul2021.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuApr2021.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuapr2022.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpujul2022.html [Third Party Advisory]
https://www.oracle.com/security-alerts/cpuoct2021.html [Third Party Advisory]
https://www.tenable.com/security/tns-2021-05 [Third Party Advisory]
https://www.tenable.com/security/tns-2021-06 [Third Party Advisory]
https://www.tenable.com/security/tns-2021-09 [Third Party Advisory]
https://www.tenable.com/security/tns-2021-10 [Third Party Advisory]

Authoritative record: CVE-2021-3449 at cve.org

Vendors: openssl

Weaknesses: CWE-476

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-3449 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.