#VU27061 NULL pointer dereference in OpenSSL - CVE-2020-1967

Vulnerability identifier: #VU27061

Vulnerability risk: Medium

CVSSv4.0: 7.7 [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-2020-1967

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
OpenSSL
Server applications / Encryption software

Vendor: OpenSSL Software Foundation

Description

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

The vulnerability exists due to a NULL pointer dereference error within the SSL_check_chain() function during or after a TLS 1.3 handshake. A remote attacker can send an invalid or unrecognised signature algorithm and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenSSL: 1.1.1d - 1.1.1f

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External links
https://www.openssl.org/news/secadv/20200421.txt

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.