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CVE-2021-20305

8.1 · HIGH

A flaw was found in Nettle in versions before 3.7.2, where several Nettle signature verification functions (GOST DSA, EDDSA & ECDSA) result in the Elliptic Curve Cryptography point (ECC) multiply f…

Published Apr 5, 2021CWE-327EPSS 1.74%

Overview

CVE-2021-20305 is a high-severity vulnerability. It was published on April 5, 2021 and has a CVSS 3.1 base score of 8.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

A flaw was found in Nettle in versions before 3.7.2, where several Nettle signature verification functions (GOST DSA, EDDSA & ECDSA) result in the Elliptic Curve Cryptography point (ECC) multiply function being called with out-of-range scalers, possibly resulting in incorrect results. This flaw allows an attacker to force an invalid signature, causing an assertion failure or possible validation. The highest threat to this vulnerability is to confidentiality, integrity, as well as system availability.

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.redhat.com/show_bug.cgi?id=1942533Reflists.debian.org/debian-lts-announce/2021/09/msg00008.htmlReflists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQKWVVMAIDAJ7YAA3VVO32BHLDOH2E63/Refsecurity.gentoo.org/glsa/202105-31Refsecurity.netapp.com/advisory/ntap-20211022-0002/Refwww.debian.org/security/2021/dsa-4933Refbugzilla.redhat.com/show_bug.cgi?id=1942533Reflists.debian.org/debian-lts-announce/2021/09/msg00008.htmlReflists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQKWVVMAIDAJ7YAA3VVO32BHLDOH2E63/Refsecurity.gentoo.org/glsa/202105-31

How CyberStrike helps

Frequently asked questions

What is CVE-2021-20305?

CVE-2021-20305 is a high-severity vulnerability. It was published on April 5, 2021 and has a CVSS 3.1 base score of 8.1 (HIGH).

How severe is CVE-2021-20305?

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2021-20305?

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-2021-20305?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-20305 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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