CVE-2020-36843: Eddsa Ed25519 Signature Malleability Vulnerability

MODERATE
Advisory Identifier: GHSA-p53j-g8pw-4w5f
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CVSS 4.3
CWE-347
Published
Advisory Summary

CVE-2020-36843 is a MODERATE (CVSS 4.3) ed25519 signature malleability vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting Eddsa libraries in the Maven ecosystem. The issue involves ed25519 signature malleability in ed25519-java due to missing scalar range check. Remediation is available by upgrading affected packages to version 0.9.39.

CVE-2020-36843 at a Glance

CVE Identifier CVE-2020-36843
GHSA Identifier GHSA-p53j-g8pw-4w5f
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product Eddsa
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2020-36843

To remediate this vulnerability, upgrade all affected Eddsa dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

net.i2p.crypto:eddsa fixed: Latest secure release 
<dependency>
    <groupId>net.i2p.crypto</groupId>
    <artifactId>eddsa</artifactId>
    <version>Latest secure release</version>
</dependency>
net.i2p:i2p fixed: 0.9.39 
<dependency>
    <groupId>net.i2p</groupId>
    <artifactId>i2p</artifactId>
    <version>0.9.39</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=net.i2p.crypto

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2020-36843, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=net.i2p.crypto

Analyze the terminal output to locate any version of Eddsa in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.9.39), your application is affected.

Note: The mvn dependency:tree -Dincludes=net.i2p.crypto command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In Eddsa, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

The implementation of EdDSA in EdDSA-Java (aka ed25519-java) through 0.3.0 exhibits signature malleability and does not satisfy the SUF-CMA (Strong Existential Unforgeability under Chosen Message Attacks) property. This allows attackers to create new valid signatures different from previous signatures for a known message.

CVE-2020-36843 Affected Eddsa Versions

2 component(s)
Fixed Versions:
0.9.39
Product / Package Ecosystem Affected Versions Fixed Version
net.i2p.crypto:eddsa
maven/net.i2p.crypto/eddsa
Maven
≤ 0.3.0
net.i2p:i2p
maven/net.i2p/i2p
Maven
< 0.9.39
0.9.39

References

NVD — CVE-2020-36843 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-36843
Eddsa Source Repository REPOSITORY
https://github.com/str4d/ed25519-java/issues/82#issue-727629226
Security Fix Commit FIX COMMIT
https://github.com/i2p/i2p.i2p/commit/d7d1dcb5399c61cf2916ccc45aa25b0209c88712#diff-658f7b1aa34b58d27796fccdb8b756c72702d64ae44703374960f1cb89a5a5c3
eprint.iacr.org/2020/1244 WEB
https://eprint.iacr.org/2020/1244
Eddsa Source Repository REPOSITORY
https://github.com/str4d/ed25519-java

Frequently Asked Questions

What is CVE-2020-36843?
CVE-2020-36843 is a security vulnerability in Eddsa involving Ed25519 Signature Malleability in ed25519-java Due to Missing Scalar Range Check under CWE-347: Improper Verification of Cryptographic Signature.
Which Eddsa versions are affected?
Affected versions include releases prior to 0.9.39 across affected packages: net.i2p.crypto:eddsa, net.i2p:i2p.
What version fixes CVE-2020-36843?
Upgrading to 0.9.39 (or the latest patched release for your respective branch) resolves the vulnerability.
Is eddsa affected?
Yes, net.i2p.crypto:eddsa is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
Is i2p affected?
Yes, net.i2p:i2p is affected in releases prior to 0.9.39. Upgrade your dependency to 0.9.39 or later.
What is the CVSS score of CVE-2020-36843?
CVE-2020-36843 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N.
What CWE is associated with CVE-2020-36843?
CVE-2020-36843 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check Maven dependencies for CVE-2020-36843?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=net.i2p.crypto'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-p53j-g8pw-4w5f",
  "modified" : "2025-03-13T16:24:28Z",
  "published" : "2025-03-13T06:30:34Z",
  "aliases" : [ "CVE-2020-36843" ],
  "summary" : "Ed25519 Signature Malleability in ed25519-java Due to Missing Scalar Range Check",
  "details" : "The implementation of EdDSA in EdDSA-Java (aka ed25519-java) through 0.3.0 exhibits signature malleability and does not satisfy the SUF-CMA (Strong Existential Unforgeability under Chosen Message Attacks) property. This allows attackers to create new valid signatures different from previous signatures for a known message.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "net.i2p.crypto:eddsa"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.3.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "net.i2p:i2p"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.9.39"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-36843"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/str4d/ed25519-java/issues/82#issue-727629226"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/i2p/i2p.i2p/commit/d7d1dcb5399c61cf2916ccc45aa25b0209c88712#diff-658f7b1aa34b58d27796fccdb8b756c72702d64ae44703374960f1cb89a5a5c3"
  }, {
    "type" : "WEB",
    "url" : "https://eprint.iacr.org/2020/1244"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/str4d/ed25519-java"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-03-13T16:24:28Z",
    "nvd_published_at" : "2025-03-13T06:15:34Z"
  }
}