FastGPT safe axios SSRF guard still allows DNS rebinding TOCTOU on protected outbound requests

FastGPT is an open-source LLM platform for building AI applications on a knowledge base. Prior to 4.15.2, the safe Axios request interceptor in packages/service/common/api/axios.ts validates a hostname with isInternalAddress() before a later HTTP connection performs an independent DNS lookup, creating a DNS rebinding window, allowing an attacker-controlled hostname to resolve publicly during the check and to a loopback, private, link-local, or metadata address during connection. An authenticated attacker who can supply a URL to a safe-Axios-backed HTTP tool, workflow HTTP node, external file fetch, or other server-side integration can use this time-of-check/time-of-use gap to reach services that direct private-address inputs would block. The same independent re-resolution occurs after manual redirect hops because each redirect target is checked before a separate connection lookup. This issue is fixed in version 4.15.2.

Source published

22 Sep 2026 16:50:19 UTC

Source modified

25 Sep 2026 23:45:50 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 6.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N