An issue was discovered 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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-24659
• https://gitlab.com/gnutls/gnutls/-/issues/1071
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/62BUAI4FQQLG6VTKRT7SUZPGJJ4NASQ3/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/AWN56FDLQQXT2D2YHNI4TYH432TDMQ7N/
• https://security.gentoo.org/glsa/202009-01
• https://security.netapp.com/advisory/ntap-20200911-0006/
• https://usn.ubuntu.com/4491-1/
• https://www.gnutls.org/security-new.html#GNUTLS-SA-2020-09-04
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00054.html
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00060.html