CVE-2026-3958 is a server-side request forgery vulnerability affecting Woahai321 ListSync versions 0.6.0 through 0.6.6. The vulnerability resides in the requests.post function call within the JSON Handler component (file list-sync-main/api_server.py). An attacker can manipulate input parameters that are passed to this function, causing the server to send crafted HTTP requests to arbitrary destinations. This can lead to unauthorized internal network scanning, access to internal services, or interaction with external malicious endpoints. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges or user interaction required, and limited impact on confidentiality, integrity, and availability. Despite early reporting, the vendor has not issued a patch or response, and no public exploit code is currently confirmed in the wild. This leaves organizations using affected versions exposed to potential SSRF attacks that could be leveraged for further internal network compromise or data exfiltration.

The SSRF vulnerability in ListSync can allow attackers to coerce the vulnerable server into making arbitrary HTTP requests. This can lead to several impacts: unauthorized access to internal network resources that are otherwise inaccessible externally, potential data leakage if internal services respond with sensitive information, and use as a pivot point for further attacks within an organization's network. Additionally, attackers might exploit this to interact with external malicious servers to exfiltrate data or trigger denial-of-service conditions. While the direct impact on confidentiality, integrity, and availability is limited, the SSRF can serve as a stepping stone for more severe attacks, especially in environments where internal services trust the vulnerable server. Organizations relying on ListSync for synchronization tasks may face operational disruptions if exploited. The lack of vendor response and patch increases the window of exposure, raising the risk for organizations worldwide.

Given the absence of an official patch, organizations should implement immediate compensating controls. First, restrict outbound HTTP requests from the ListSync server using network-level controls such as firewall rules or proxy filtering to limit destinations to only trusted endpoints. Implement input validation and sanitization on any user-controllable parameters that influence requests.post calls to prevent injection of arbitrary URLs. Employ web application firewalls (WAFs) with SSRF detection capabilities to monitor and block suspicious request patterns. Monitor logs for unusual outbound request activity originating from ListSync components. Consider isolating the ListSync server within a segmented network zone with minimal access to internal resources. If feasible, temporarily discontinue use of vulnerable ListSync versions until a vendor patch is available. Engage with the vendor or community for updates and apply patches promptly once released. Additionally, conduct internal security assessments to identify any potential exploitation attempts and remediate accordingly.