CVE-2020-26961 Explained : Impact and Mitigation

A vulnerability in Firefox, Firefox ESR, and Thunderbird could allow a DNS Rebinding attack when using DNS over HTTPS.

Understanding CVE-2020-26961

This CVE involves a flaw in the filtering mechanism of DNS over HTTPS (DoH) that could lead to a potential security risk.

What is CVE-2020-26961?

When IPv4 addresses are mapped through IPv6, the filtering mechanism of DoH fails to block them, potentially enabling a DNS Rebinding attack.

The Impact of CVE-2020-26961

This vulnerability affects users of Firefox versions prior to 83, Firefox ESR versions prior to 78.5, and Thunderbird versions prior to 78.5.

Technical Details of CVE-2020-26961

This section provides more in-depth technical information about the vulnerability.

Vulnerability Description

The flaw allows IPv4 addresses mapped through IPv6 to bypass DoH filtering, creating a potential security risk for users.

Affected Systems and Versions

Firefox < 83
Firefox ESR < 78.5
Thunderbird < 78.5

Exploitation Mechanism

Attackers could exploit this vulnerability to conduct DNS Rebinding attacks, potentially compromising user security.

Mitigation and Prevention

To address CVE-2020-26961, users and organizations should take immediate and long-term security measures.

Immediate Steps to Take

Update Firefox, Firefox ESR, and Thunderbird to versions 83, 78.5, and 78.5 respectively.
Avoid using DoH until the software is updated.

Long-Term Security Practices

Regularly update software to the latest versions.
Implement network security measures to detect and prevent DNS Rebinding attacks.

Patching and Updates

Apply patches provided by Mozilla to fix the vulnerability and enhance system security.