CVE-2026-42344 MEDIUM

CVE-2026-42344: FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints

Vendor Labring
Product FastGPT
Weakness CWE-367
Published May 8, 2026
Last update May 11, 2026
View on NVD All CVEs

CVSS base score

6.3/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality High
Integrity None

CVSS vector

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

What the vulnerability does

01Description

FastGPT is an AI Agent building platform. In versions 4.14.11 and prior, FastGPT's isInternalAddress() function in packages/service/common/system/utils.ts is vulnerable to DNS rebinding (TOCTOU — Time-of-Check to Time-of-Use). The function resolves the hostname via dns.resolve4()/dns.resolve6() and checks resolved IPs against private ranges, but the actual HTTP request happens in a separate call with a new DNS resolution, allowing the DNS record to change between validation and fetch. At time of publication, there are no publicly available patches.

Key dates

02Disclosure timeline

May 8, 2026 CVE published
May 11, 2026 Record updated