What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-08 · updated 2026-07-24
• Weakness: CWE-367

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.

Affected products

• labring FastGPT: through 4.14.11

References

• https://github.com/labring/FastGPT/security/advisories/GHSA-cc8x-jrqv-hmwh
• https://github.com/labring/FastGPT/security/advisories/GHSA-cc8x-jrqv-hmwh

Get alerted when CVE-2026-42344 or the next vulnerability affects your stack