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Vulnerabilities

Vulnerability · CVE-2021-20305

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 Crypt…

Published Apr 5, 2021 · catalog updated Oct 14, 2026 · nettle project

Check if you run it

No confirmed exploitation is on record for CVE-2021-20305. EPSS is 1.74%. Act only if a listed version of nettle project is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.74%
Remediation
Advisory link
Affected products
cpe debian/debian linux · cpe fedoraproject/fedora · cpe netapp/active iq unified manager · cpe netapp/ontap select deploy administration utility · cpe nettle project/nettle · cpe redhat/enterprise linux

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe debian/debian linux10.0
  • cpe debian/debian linux9.0
  • cpe fedoraproject/fedora33
  • cpe netapp/active iq unified managerversion unspecified
  • cpe netapp/ontap select deploy administration utilityversion unspecified
  • cpe nettle project/nettleversion unspecified
  • cpe redhat/enterprise linux7.0
  • cpe redhat/enterprise linux8.0

How to fix CVE-2021-20305

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-20305. EPSS is 1.74%. Act only if a listed version of nettle project is installed.

Which versions are affected?

Compare what you have installed with debian/debian linux 10.0; debian/debian linux 9.0; redhat/enterprise linux 7.0; redhat/enterprise linux 8.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-327: Use of a Broken or Risky Cryptographic Algorithm; CWE-787: Out-of-bounds Write. EPSS 1.74%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 5, 2021 · NIST NVD

    Detected

    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. T

  2. Oct 14, 2026 · NIST NVD

    Updated

    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. T

Sources

  • CVE.orgVulnerability recordCVE-2021-20305

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-20305

    30-day exploitation probability 1.7%

    first.org
  • NIST NVDVulnerability recordCVE-2021-20305

    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 res

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 16, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.