CVE-2026-85738: TREK: SSRF Guard Bypass via IPv6 Transition Addresses (NAT64/6to4)
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
TREKto a version that resolves this vulnerability.Fixed in 3.4.0
Event History
Frequently Asked Questions
Which deployments are practically exposed to this issue?
Deployments running TREK before 3.4.0 are exposed where a user-facing import, webhook, integration, or plugin can make outbound requests and the environment routes the relevant NAT64, 6to4, or Teredo address format. The impact can include access to internal services or cloud metadata and disclosure of returned information.
What does an attacker need to exploit the bypass?
The attacker needs an authenticated TREK account and control of a DNS record. They must cause the supplied URL to resolve through an AAAA record to a supported IPv6 transition address that embeds a private, loopback, or link-local IPv4 destination.
Are ordinary IPv6 destinations the issue?
No. The described bypass specifically relies on NAT64, 6to4, or Teredo IPv6 transition addresses that encode an IPv4 target and are incorrectly classified as allowed by the SSRF checks.
How can this be remediated?
Upgrade TREK to version 3.4.0, which fixes the issue. The provided data does not describe a separate workaround for deployments that cannot immediately upgrade.