CVE-2026-40100 labring CVE debrief

Who should care

Defenders responsible for FastGPT instances, especially those with publicly accessible APIs, should assess exposure and apply the patch to prevent SSRF attacks. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify the exposure of FastGPT instances and review compensating controls for exposed systems.

Why it matters

CVE-2026-40100 is a Server-Side Request Forgery (SSRF) vulnerability in FastGPT that allows unauthenticated attackers to access internal network resources. Defenders should prioritize verifying exposure and applying the patch.

• Unauthenticated attackers can perform SSRF against internal network resources
• Internal network resources may be accessed without authentication
• Defenders need to verify exposure of FastGPT instances and apply the patch

Technical summary

The /api/core/app/mcpTools/runTool endpoint in FastGPT accepts arbitrary URLs without authentication, allowing unauthenticated attackers to perform SSRF against internal network resources. The internal IP check only blocks private IPs when CHECK_INTERNAL_IP=true, which is not the default. This vulnerability allows unauthenticated attackers to access internal network resources, and defenders should prioritize verifying exposure of FastGPT instances, especially those with publicly accessible APIs, and apply the patch to prevent SSRF attacks.

Defensive priority

Defenders should prioritize verifying exposure of FastGPT instances, especially those with publicly accessible APIs, and apply the patch to prevent SSRF attacks.

Recommended defensive actions

• Verify exposure of FastGPT instances, especially those with publicly accessible APIs
• Apply the patch to prevent SSRF attacks
• Monitor for suspicious activity on internal network resources
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected versions. A vendor advisory is also available on GitHub. Defenders should verify the exposure of FastGPT instances, especially those with publicly accessible APIs, and review compensating controls for exposed systems while remediation is scheduled and verified.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.