Summary
The Thinbus Javascript Secure Remote Password (SRP) Client Generates Fewer Bits of Entropy Than Intended
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;
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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-54885? CVE-2025-54885 is a medium-severity security vulnerability in thinbus-srp (npm), affecting versions < 2.0.1. It is fixed in 2.0.1.
- Which versions of thinbus-srp are affected by CVE-2025-54885? thinbus-srp (npm) versions < 2.0.1 is affected.
- Is there a fix for CVE-2025-54885? Yes. CVE-2025-54885 is fixed in 2.0.1. Upgrade to this version or later.
- Is CVE-2025-54885 exploitable, and should I be worried? Whether CVE-2025-54885 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-54885 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-54885? Upgrade
thinbus-srpto 2.0.1 or later.