CVE-2025-54885
Thinbus generates insufficient entropy: 252 bits vs minimum 256 bits
Thinbus Javascript Secure Remote Password is a browser SRP6a implementation for zero-knowledge password authentication. In versions 2.0.0 and below, a protocol compliance bug causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof. This is fixed in version 2.0.1.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Thinbus generates insufficient entropy: 252 bits vs minimum 256 bits
Thinbus Javascript Secure Remote Password is a browser SRP6a implementation for zero-knowledge password authentication. In versions 2.0.0 and below, a protocol compliance bug causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof. This is fixed in version 2.0.1.
- Record
CVE-2025-54885- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-331
- Updated
- 2026-11-02
EUVDEUVD-2025-23897
Thinbus Javascript Secure Remote Password is a browser SRP6a implementation for zero-knowledge password authentication. In versions 2.0.0 and below, a protocol compliance bug causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof. This is fixed in version 2.0.1.
- Record
EUVD-2025-23897- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-8q6v-474h-whgg
The Thinbus Javascript Secure Remote Password (SRP) Client Generates Fewer Bits of Entropy Than Intended
Impact
A protocol compliance bug in thinbus-srp-npm versions prior to 2.0.1 causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). RFC 5054 states in section 2.5.4 Client Key Exchange
The client key exchange message carries the client's public value (A). The client calculates this value as A = g^a % N, where a is a random number that SHOULD be at least 256 bits in length.
The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof.
Patches
The issue is fixed in versions >= 2.0.1
Workarounds
It is possible to patch a legacy version:
// WRONG
var hexLength = this.toHex(N).length;
// CORRECT
var hexLength = this.toHex(this.N()).length;
- Record
GHSA-8q6v-474h-whgg- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-331
- Updated
- 2026-11-02
NVD
Thinbus Javascript Secure Remote Password is a browser SRP6a implementation for zero-knowledge password authentication. In versions 2.0.0 and below, a protocol compliance bug causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof. This is fixed in version 2.0.1.
- Record
CVE-2025-54885- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Weakness
- CWE-331
- Updated
- 2026-11-02
OSV
Thinbus generates insufficient entropy: 252 bits vs minimum 256 bits
Thinbus Javascript Secure Remote Password is a browser SRP6a implementation for zero-knowledge password authentication. In versions 2.0.0 and below, a protocol compliance bug causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof. This is fixed in version 2.0.1.
- Record
CVE-2025-54885- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-331
- Updated
- 2026-11-02
OSVGHSA-8q6v-474h-whgg
The Thinbus Javascript Secure Remote Password (SRP) Client Generates Fewer Bits of Entropy Than Intended
Impact
A protocol compliance bug in thinbus-srp-npm versions prior to 2.0.1 causes the client to generate a fixed 252 bits of entropy instead of the intended bit length of the safe prime (defaulted to 2048 bits). RFC 5054 states in section 2.5.4 Client Key Exchange
The client key exchange message carries the client's public value (A). The client calculates this value as A = g^a % N, where a is a random number that SHOULD be at least 256 bits in length.
The client public value is being generated from a private value that is 4 bits below the specification. This reduces the protocol's designed security margin it is now practically exploitable. The servers full sized 2048 bit random number is used to create the shared session key and password proof.
Patches
The issue is fixed in versions >= 2.0.1
Workarounds
It is possible to patch a legacy version:
// WRONG
var hexLength = this.toHex(N).length;
// CORRECT
var hexLength = this.toHex(this.N()).length;
- Record
GHSA-8q6v-474h-whgg- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-331
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
thinbus-srpnpm |
before 2.0.1 | 2.0.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-54885 is a medium vulnerability (CVSS 6.9) in Simbo1905 Thinbus-srp-npm, published August 6, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in thinbus-srp 2.0.1.
References
github.com/simbo1905/thinbus-srp-npm/security/advisories/GHSA-8q6v-474h-whgg
nvd.nist.gov/vuln/detail/CVE-2025-54885