CVE-2026-42344: CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition in labring FastGPT
CVE-2026-42344 is a medium severity vulnerability in labring FastGPT versions 4. 14. 11 and earlier. It involves a Time-of-Check to Time-of-Use (TOCTOU) race condition in the isInternalAddress() function, which performs DNS resolution to validate IP addresses before making HTTP requests. Because the DNS resolution is done twice separately, an attacker can exploit DNS rebinding to change the resolved IP between the check and the actual request, potentially bypassing IP-based access controls. No patches or official fixes are available at the time of publication.
AI Analysis
Technical Summary
FastGPT's isInternalAddress() function resolves hostnames using dns.resolve4()/dns.resolve6() to check if the IP addresses belong to private ranges. However, the actual HTTP request uses a separate DNS resolution, allowing the DNS record to change between the validation and the request. This TOCTOU race condition can be exploited via DNS rebinding attacks to bypass internal address checks. The vulnerability affects FastGPT versions up to 4.14.11. There are no known public exploits or patches currently.
Potential Impact
Successful exploitation could allow an attacker to bypass internal IP address restrictions by manipulating DNS responses between the check and use phases. This could lead to unauthorized access to internal resources or sensitive data. The CVSS score of 6.3 reflects a medium severity with high confidentiality impact but no integrity or availability impact. No known exploits are reported in the wild.
Mitigation Recommendations
At the time of publication, no official patches or fixes are available. Users should monitor vendor advisories for updates. Until a fix is released, consider implementing network-level protections to restrict DNS rebinding attacks or avoid using vulnerable versions in sensitive environments.
CVE-2026-42344: CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition in labring FastGPT
Description
CVE-2026-42344 is a medium severity vulnerability in labring FastGPT versions 4. 14. 11 and earlier. It involves a Time-of-Check to Time-of-Use (TOCTOU) race condition in the isInternalAddress() function, which performs DNS resolution to validate IP addresses before making HTTP requests. Because the DNS resolution is done twice separately, an attacker can exploit DNS rebinding to change the resolved IP between the check and the actual request, potentially bypassing IP-based access controls. No patches or official fixes are available at the time of publication.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
FastGPT's isInternalAddress() function resolves hostnames using dns.resolve4()/dns.resolve6() to check if the IP addresses belong to private ranges. However, the actual HTTP request uses a separate DNS resolution, allowing the DNS record to change between the validation and the request. This TOCTOU race condition can be exploited via DNS rebinding attacks to bypass internal address checks. The vulnerability affects FastGPT versions up to 4.14.11. There are no known public exploits or patches currently.
Potential Impact
Successful exploitation could allow an attacker to bypass internal IP address restrictions by manipulating DNS responses between the check and use phases. This could lead to unauthorized access to internal resources or sensitive data. The CVSS score of 6.3 reflects a medium severity with high confidentiality impact but no integrity or availability impact. No known exploits are reported in the wild.
Mitigation Recommendations
At the time of publication, no official patches or fixes are available. Users should monitor vendor advisories for updates. Until a fix is released, consider implementing network-level protections to restrict DNS rebinding attacks or avoid using vulnerable versions in sensitive environments.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-26T13:26:14.515Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69fe61e5cbff5d8610367fb2
Added to database: 5/8/2026, 10:21:25 PM
Last enriched: 5/8/2026, 10:36:55 PM
Last updated: 5/9/2026, 1:00:05 AM
Views: 7
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