Session compromise via undersized client ephemeral secret
Published Aug 7, 2025 · Updated Aug 7, 2025
Insufficient entropy in Simon Massey's thinbus-srp before 2.0.1 allows remote attackers to compromise SRP session confidentiality and integrity. The client randomA() path passes the BigInteger constructor N, rather than the actual prime from this.N(), to toHex(), fixing the private ephemeral value at 63 hexadecimal characters, or 252 bits. Network exploitation requires high-complexity cryptanalysis against an authentication exchange; the server still contributes a full-size 2048-bit random value to the shared key and proof.
Summary
What happened
Insufficient entropy in Simon Massey's thinbus-srp before 2.0.1 allows remote attackers to compromise SRP session confidentiality and integrity. The client randomA() path passes the BigInteger constructor N, rather than the actual prime from this.N(), to toHex(), fixing the private ephemeral value at 63 hexadecimal characters, or 252 bits. Network exploitation requires high-complexity cryptanalysis against an authentication exchange; the server still contributes a full-size 2048-bit random value to the shared key and proof.
The record
- CVE
- CVE-2025-54885
- Published
- Aug 7, 2025
- Updated
- Aug 7, 2025
- Vendor
- Simon Massey
- Product
- thinbus-srp
- Classifications
- CWE-331, CAPEC-59
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 7, 2025CVE publishedPublication date reported by the CVE source.
- Aug 7, 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?
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- Affected versionversion=< 2.0.1
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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