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CVE-2020-26961

6.5 · MEDIUM

When DNS over HTTPS is in use, it intentionally filters RFC1918 and related IP ranges from the responses as these do not make sense coming from a DoH resolver.

Published Dec 9, 2020EPSS 1.17%

Overview

CVE-2020-26961 is a medium-severity vulnerability. It was published on December 9, 2020 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

When DNS over HTTPS is in use, it intentionally filters RFC1918 and related IP ranges from the responses as these do not make sense coming from a DoH resolver. However when an IPv4 address was mapped through IPv6, these addresses were erroneously let through, leading to a potential DNS Rebinding attack. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refbugzilla.mozilla.org/show_bug.cgi?id=1672528Refwww.mozilla.org/security/advisories/mfsa2020-50/Refwww.mozilla.org/security/advisories/mfsa2020-51/Refwww.mozilla.org/security/advisories/mfsa2020-52/Refbugzilla.mozilla.org/show_bug.cgi?id=1672528Refwww.mozilla.org/security/advisories/mfsa2020-50/Refwww.mozilla.org/security/advisories/mfsa2020-51/Refwww.mozilla.org/security/advisories/mfsa2020-52/

How CyberStrike helps

Frequently asked questions

What is CVE-2020-26961?

CVE-2020-26961 is a medium-severity vulnerability. It was published on December 9, 2020 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2020-26961?

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2020-26961?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2020-26961?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2020-26961 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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