#VU51733 NULL pointer dereference in OpenSSL - CVE-2021-3449

Vulnerability identifier: #VU51733

Vulnerability risk: Medium

CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/U:Green

CVE-ID: CVE-2021-3449

CWE-ID: CWE-476

Exploitation vector: Remote access

Exploit availability: Public exploit is available

Vulnerable software:
OpenSSL

Software vendor:
OpenSSL Software Foundation

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error when processing TLSv1.2 renegotiations. A remote attacker can send a maliciously crafted renegotiation ClientHello message, which omits the signature_algorithms extension but includes a signature_algorithms_cert extension, trigger a NULL pointer dereference error and crash the server.

Install update from vendor's website.

• https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=fb9fa6b51defd48157eeb207f52181f735d96148
• https://www.openssl.org/news/secadv/20210325.txt