CVE-2026-42344: FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
FastGPTto a version that resolves this vulnerability.Fixed in 4.14.11 - Compensating control
Mitigate DNS rebinding/TOCTOU by preventing FastGPT from making HTTP requests to internal/private IP ranges that could be reached via attacker-controlled DNS (e.g., enforce network egress controls so requests to private ranges are blocked).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42344?
CVE-2026-42344 is considered a high severity vulnerability due to its potential for server-side request forgery (SSRF) attacks on protected endpoints.
How do I fix CVE-2026-42344?
To fix CVE-2026-42344, update FastGPT to version 4.14.12 or later to mitigate the DNS rebinding vulnerability.
What are the potential impacts of CVE-2026-42344?
The potential impacts of CVE-2026-42344 include unauthorized access to sensitive endpoints and data exposure through SSRF.
Which versions of FastGPT are affected by CVE-2026-42344?
FastGPT versions up to and including 4.14.11 are affected by CVE-2026-42344.
What is the attack vector for CVE-2026-42344?
The attack vector for CVE-2026-42344 is DNS rebinding that allows attackers to exploit the isInternalAddress function.