CVE-2026-42344 FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints
Attackers can bypass internal address checks via DNS rebinding to perform Server-Side Request Forgery on protected endpoints in FastGPT.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42344?
CVE-2026-42344 is a medium-severity server-side request forgery vulnerability in labring FastGPT, published on 8 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-367
Which versions are affected by CVE-2026-42344?
How do I fix CVE-2026-42344?
No fix has been published for CVE-2026-42344 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-42344 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42344 exists.
Sources
Also known as GHSA-cc8x-jrqv-hmwh.