NULL pointer deref in signature_algorithms processing

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).

Scores

EPSS (exploitation in 30 days)

63.5% · top 0.8% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.9.

Weakness

• NULL pointer dereference
• CWE-476 (opens in a new tab)All about CWE-476 and its CVEs

Affected products

• OpenSSL · OpenSSL

  • affected Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j)

Affected packages

From reviewed advisories of the GitHub Advisory Database.

• crates.ioopenssl-srcGHSA-83mx-573x-5rw9 (opens in a new tab)

References (29)

• https://www.openssl.org/news/secadv/20210325.txt (opens in a new tab)x_transferred
• https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=fb9fa6b51defd48157eeb207f52181f735d96148 (opens in a new tab)x_transferred
• 20210325 Multiple Vulnerabilities in OpenSSL Affecting Cisco Products: March 2021 (opens in a new tab)vendor-advisoryx_transferred
• DSA-4875 (opens in a new tab)vendor-advisoryx_transferred
• [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 (opens in a new tab)mailing-listx_transferred
• [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 (opens in a new tab)mailing-listx_transferred
• [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 (opens in a new tab)mailing-listx_transferred
• [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 (opens in a new tab)mailing-listx_transferred
• GLSA-202103-03 (opens in a new tab)vendor-advisoryx_transferred
• FEDORA-2021-cbf14ab8f9 (opens in a new tab)vendor-advisoryx_transferred
• https://www.oracle.com/security-alerts/cpuApr2021.html (opens in a new tab)x_transferred
• https://www.tenable.com/security/tns-2021-10 (opens in a new tab)x_transferred
• https://www.tenable.com/security/tns-2021-09 (opens in a new tab)x_transferred
• https://security.netapp.com/advisory/ntap-20210513-0002/ (opens in a new tab)x_transferred
• https://security.netapp.com/advisory/ntap-20210326-0006/ (opens in a new tab)x_transferred
• https://security.FreeBSD.org/advisories/FreeBSD-SA-21:07.openssl.asc (opens in a new tab)x_transferred
• https://www.tenable.com/security/tns-2021-06 (opens in a new tab)x_transferred
• https://www.tenable.com/security/tns-2021-05 (opens in a new tab)x_transferred
• https://kc.mcafee.com/corporate/index?page=content&id=SB10356 (opens in a new tab)x_transferred
• https://www.oracle.com//security-alerts/cpujul2021.html (opens in a new tab)x_transferred
• https://cert-portal.siemens.com/productcert/pdf/ssa-772220.pdf (opens in a new tab)x_transferred
• https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44845 (opens in a new tab)x_transferred
• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0013 (opens in a new tab)x_transferred
• [debian-lts-announce] 20210831 [SECURITY] [DLA 2751-1] postgresql-9.6 security update (opens in a new tab)mailing-listx_transferred
• https://www.oracle.com/security-alerts/cpuoct2021.html (opens in a new tab)x_transferred
• https://www.oracle.com/security-alerts/cpuapr2022.html (opens in a new tab)x_transferred
• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf (opens in a new tab)x_transferred
• https://www.oracle.com/security-alerts/cpujul2022.html (opens in a new tab)x_transferred
• https://security.netapp.com/advisory/ntap-20240621-0006/ (opens in a new tab)x_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisory GHSA-83mx-573x-5rw9 (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-3449](https://trackcve.app/badge/CVE-2021-3449.svg)](https://trackcve.app/cve/CVE-2021-3449)

Record last updated 8 Oct 2026, 21:13 UTC.