CVE•Published 2021-04-05•Modified 2026-10-14•1 article on news•4 live references•NVD data

CVE-2021-20305Nettle_project · Nettle

Vulnerability data via NVD (ingested)

CVSS v3.1

8.1

HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS percentile

Exploit Prediction Scoring System · top 24% of all CVEs

Weaknesses (CWE)

CWE-327Use of a Broken or Risky Cryptographic Algorithm CWE-787Out-of-bounds Write

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.

Timeline

Published 2021-04-05

Modified 2026-10-14

External references

NVD MITRE trickest/cve VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag3 hosts

vuln:CVE-2021-20305

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Nettle Project Nettle"

All exposed Nettle Project Nettle instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Nettle"

HTTP body or banner mentions "Nettle" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2021-20305