#VU46295 NULL pointer dereference in GnuTLS - CVE-2020-24659

Vulnerability identifier: #VU46295

Vulnerability risk: Medium

CVSSv4.0: 4.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-24659

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
GnuTLS
Universal components / Libraries / Libraries used by multiple products

Vendor: GnuTLS

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 in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure. A remote attacker can perform a denial of service (DoS) attack.

Mitigation
Update to version 3.6.15.

Vulnerable software versions

GnuTLS: 3.6.0 - 3.6.14

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External links
https://gitlab.com/gnutls/gnutls/-/issues/1071
https://security.gentoo.org/glsa/202009-01
https://www.gnutls.org/security-new.html#GNUTLS-SA-2020-09-04

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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.