MitM attack in GnuTLS

Published: 2020-06-04
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2020-13777
Exploitation vector Local network
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
Universal components / Libraries / Libraries used by multiple products

Vendor GnuTLS

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Man-in-the-Middle (MitM) attack

EUVDB-ID: #VU28557

Risk: Medium

CVSSv3.1: 5.5 [CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-13777

CWE-ID: CWE-300 - Channel Accessible by Non-Endpoint ('Man-in-the-Middle')

Exploit availability: Yes


The vulnerability allows a remote attacker to perform Man-in-the-Middle (MitM) attack.

The vulnerability exists due to regression, introduced into the TLS protocol implementation that caused the TLS server to not securely construct a session ticket encryption key considering the application supplied secret. A remote attacker can bypass authentication in TLS 1.3 and recover previous conversations in TLS 1.2


Install updates from vendor's website.

Vulnerable software versions

GnuTLS: 3.6.4, 3.6.5, 3.6.6, 3.6.7, 3.6.8, 3.6.9, 3.6.10, 3.6.11,, 3.6.12, 3.6.13

CPE2.3 External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).

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.