Signature substitution via missing scalar range check
Published Mar 13, 2025 · Updated Mar 18, 2025
Signature verification in str4d EdDSA-Java 0.3.0 and earlier allows attackers to create a new valid signature for a known message. EdDSAEngine.engineVerify accepts an Ed25519 signature without checking that scalar s is in the range [0, L), permitting an alternate signature to pass verification. Exploitation requires a previously signed message and signature; the bounded consequence is signature substitution rather than authorization to sign a different message.
Summary
What happened
Signature verification in str4d EdDSA-Java 0.3.0 and earlier allows attackers to create a new valid signature for a known message. EdDSAEngine.engineVerify accepts an Ed25519 signature without checking that scalar s is in the range [0, L), permitting an alternate signature to pass verification. Exploitation requires a previously signed message and signature; the bounded consequence is signature substitution rather than authorization to sign a different message.
The record
- CVE
- CVE-2020-36843
- Published
- Mar 13, 2025
- Updated
- Mar 18, 2025
- Vendor
- str4d
- Product
- EdDSA-Java
- Classifications
- CWE-347
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 13, 2025CVE publishedPublication date reported by the CVE source.
- Mar 18, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=0.3.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- ed25519-speccheck malleability test vectorsproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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