CVE-2021-20305: Debian Linux

High severity, CVSS 8.1. EPSS: 1.7% chance of exploitation in the next 30 days.

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.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 33 only
• Netapp Active Iq Unified Manager: affected versions not specified
• Netapp Ontap Select Deploy Administration Utility: affected versions not specified
• Nettle Project Nettle: before 3.7.2 (fixed in 3.7.2)
• Red Hat Enterprise Linux: version 7.0 only; version 8.0 only

Published 2021-04-05. Last modified 2026-06-17.