CVE-2026-3958 is a server-side request forgery vulnerability identified in the Woahai321 ListSync software, specifically affecting versions 0.6.0 through 0.6.6. The flaw exists in the requests.post function call within the list-sync-main/api_server.py file, part of the JSON Handler component. SSRF vulnerabilities allow attackers to induce the server to send crafted HTTP requests to arbitrary destinations, potentially bypassing firewall restrictions and accessing internal services or sensitive data. This vulnerability can be exploited remotely without requiring authentication or user interaction, increasing its risk profile. The vulnerability was responsibly disclosed to the project maintainers, but no patch or official response has been released as of the publication date. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, and low to limited impact on confidentiality, integrity, and availability. While no active exploits have been reported in the wild, the public disclosure of the exploit code increases the likelihood of exploitation attempts. The absence of a patch means organizations must rely on mitigation strategies until an official fix is available.

The SSRF vulnerability in ListSync can allow attackers to make unauthorized requests from the vulnerable server to internal or external systems. This can lead to several impacts including unauthorized access to internal network resources, bypassing network access controls, and potential information disclosure if internal services respond with sensitive data. Attackers might also use this vulnerability as a pivot point to conduct further attacks within an organization's network. Although the CVSS score is medium, the ease of remote exploitation without authentication elevates the risk, especially in environments where ListSync is exposed to untrusted networks. The vulnerability could disrupt normal operations if exploited to access or manipulate internal services, potentially impacting confidentiality and integrity of data. Organizations relying on ListSync for synchronization tasks may face operational risks and data exposure until the vulnerability is addressed.

Since no official patch is currently available, organizations should implement the following mitigations: 1) Restrict network access to the ListSync service, ensuring it is not exposed to untrusted or public networks. 2) Implement strict input validation and sanitization on any user-supplied URLs or parameters that influence requests.post calls to prevent malicious URL injection. 3) Use network segmentation and firewall rules to limit the server's ability to make outbound requests to sensitive internal resources. 4) Monitor and log outbound requests from the ListSync server to detect unusual or unauthorized request patterns. 5) If possible, deploy a web application firewall (WAF) with rules to detect and block SSRF attack patterns targeting ListSync. 6) Consider temporarily disabling or restricting the vulnerable JSON Handler functionality if feasible. 7) Stay alert for vendor updates or patches and plan for immediate deployment once available. 8) Conduct internal security assessments to identify any potential exploitation attempts and review access controls around the affected systems.