CVE-2021-20305
HIGHEPSS 74th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Elevated risk: more likely to be exploited than 74% of all known CVEs.
References
Related Vulnerabilities
Other CWE-327 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2015-2808 | Low | 3.7 | 74% | - | Fix |
| CVE-2023-34039 | Critical | 9.8 | 64% | - | Fix |
| CVE-2016-6602 | Critical | 9.8 | 55% | - | - |
| CVE-2014-8687 | Critical | 9.8 | 44% | - | - |
| CVE-2020-13777 | High | 7.4 | 18% | - | Fix |
| CVE-2017-17428 | Medium | 5.9 | 15% | - | - |
Common questions
How do I fix CVE-2021-20305?
Published advisories record a fix for 4 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-20305 being actively exploited?
Not that we know of. CVE-2021-20305 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 74% of all scored CVEs.
How severe is CVE-2021-20305?
CVE-2021-20305 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-20305 affect?
Published advisories record a fix for nettle (Debian), libnettle6 (Ubuntu), libnettle7 (Ubuntu), nettle (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.