CVE-2026-49138 is an SSRF vulnerability in the HKUDS nanobot product, specifically in the web_fetch tool. Versions before 0.2.1 are affected. The vulnerability occurs because the httpx library used by nanobot automatically follows HTTP 3xx redirects, allowing an attacker to supply a URL that redirects to loopback or private network addresses. This redirect-following behavior happens before the final resolved URL validation, enabling attackers to reach internal hosts that should be inaccessible. The vulnerability has a CVSS 4.0 base score of 5.3, indicating medium severity.

An attacker can exploit this vulnerability to make the nanobot runtime send outbound HTTP requests to internal or private network hosts that are normally not accessible externally. This can lead to unauthorized access or information disclosure within internal networks. However, there is no indication of privilege escalation, code execution, or direct data compromise beyond SSRF-based internal network access.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch is currently documented. Until a patch is available, users should consider disabling or restricting the use of the web_fetch tool or implementing network-level controls to prevent SSRF exploitation. Monitor vendor communications for updates regarding an official fix.