CVE-2026-42344CWE-367

FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints

Medium · published May 8, 2026

CVSS v3.1
6.3
EPSS
0%
Percentile
13.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00229 · 13.0th percentile
Weakness
CWE-367 · Time-of-check Time-of-use (TOCTOU) Race Condition
Published
2026-05-08T22:10Z
EPSS history
Timeline
  • 08 MAY 22:10Z
    FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints
    cvelistv5