CVE-2020-13777 : Vulnerability Insights and Analysis

GnuTLS 3.6.x before 3.6.14 has a vulnerability that affects the encryption of session tickets, leading to a loss of confidentiality in TLS 1.2 and an authentication bypass in TLS 1.3.

Understanding CVE-2020-13777

This CVE involves incorrect cryptography in GnuTLS versions prior to 3.6.14, impacting the security of TLS sessions.

What is CVE-2020-13777?

GnuTLS versions before 3.6.14 improperly handle session ticket encryption, resulting in a confidentiality loss in TLS 1.2 and an authentication bypass in TLS 1.3.

The Impact of CVE-2020-13777

The vulnerability allows attackers to compromise the confidentiality of TLS 1.2 sessions and bypass authentication in TLS 1.3, potentially leading to unauthorized access and data exposure.

Technical Details of CVE-2020-13777

GnuTLS 3.6.x before 3.6.14 is affected by incorrect cryptography for session ticket encryption.

Vulnerability Description

The flaw in GnuTLS versions prior to 3.6.14 results in incorrect encryption of session tickets, causing a loss of confidentiality in TLS 1.2 and an authentication bypass in TLS 1.3.

Affected Systems and Versions

GnuTLS versions before 3.6.14
The earliest impacted version is 3.6.4 (2018-09-24) due to an error in a 2018-09-18 commit

Exploitation Mechanism

Until the first key rotation, the TLS server consistently uses incorrect data instead of an encryption key derived from an application, leading to the encryption vulnerability.

Mitigation and Prevention

To address CVE-2020-13777, follow these steps:

Immediate Steps to Take

Update GnuTLS to version 3.6.14 or later
Monitor vendor advisories for patches and security updates

Long-Term Security Practices

Regularly update software and libraries to the latest versions
Implement secure coding practices and cryptographic protocols

Patching and Updates

Apply patches provided by GnuTLS promptly to mitigate the vulnerability