CVE-2025-51591 is a Server-Side Request Forgery (SSRF) vulnerability identified in JGM Pandoc version 3.6.4. SSRF vulnerabilities occur when an attacker can manipulate a server to make unintended requests to internal or external resources, potentially bypassing network access controls. In this case, the vulnerability arises from the ability to inject a crafted iframe, which can be used by an attacker to coerce the server into making unauthorized requests. This can lead to unauthorized access to internal infrastructure components that are otherwise inaccessible externally. The vulnerability is classified under CWE-918, which covers SSRF issues. According to the CVSS v3.1 vector, the attack vector is network-based (AV:N), with high attack complexity (AC:H), no privileges required (PR:N), and no user interaction needed (UI:N). The impact on confidentiality is high (C:H), integrity is low (I:L), and availability is none (A:N). This indicates that an attacker can potentially access sensitive data but has limited ability to modify data or disrupt services. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was published on July 11, 2025, with a medium severity score of 6.5. The lack of affected version details beyond 3.6.4 suggests that this version is the primary concern. The SSRF via iframe injection implies that the vulnerability may be exploited by submitting malicious content that causes the server to perform unintended requests, potentially exposing internal systems or sensitive information within the infrastructure.

For European organizations using JGM Pandoc 3.6.4, this SSRF vulnerability poses a significant risk to confidentiality. Attackers could leverage this flaw to access internal services, databases, or administrative interfaces that are not directly exposed to the internet, leading to potential data breaches or reconnaissance for further attacks. Given the high confidentiality impact, sensitive corporate data, intellectual property, or personal data protected under GDPR could be exposed, resulting in regulatory penalties and reputational damage. The medium severity and high attack complexity suggest that exploitation is not trivial but feasible for skilled attackers. The lack of required privileges or user interaction increases the risk of automated or remote exploitation attempts. Although integrity and availability impacts are low or none, the ability to access internal infrastructure could facilitate lateral movement or pivoting attacks, increasing overall risk. European organizations with complex internal networks or those relying heavily on JGM Pandoc for document processing or conversion services are particularly vulnerable. The absence of known exploits in the wild currently provides a window for proactive mitigation before widespread attacks occur.

1. Immediate mitigation should include restricting network access to the JGM Pandoc service, ensuring it cannot make arbitrary outbound requests to internal or external systems unless explicitly required and authorized. 2. Implement strict input validation and sanitization on any user-supplied content that could be processed by Pandoc, especially content that could include iframes or other embedded elements. 3. Use network segmentation and firewall rules to limit the server's ability to reach sensitive internal resources, reducing the impact of SSRF exploitation. 4. Monitor logs and network traffic for unusual outbound requests originating from the Pandoc server, which could indicate exploitation attempts. 5. Engage with the vendor or open-source maintainers to obtain or develop patches addressing this vulnerability, and prioritize timely deployment once available. 6. Consider deploying Web Application Firewalls (WAFs) with rules designed to detect and block SSRF attack patterns targeting the Pandoc service. 7. Conduct internal security assessments and penetration testing focusing on SSRF vectors within the document processing workflows. 8. Educate developers and system administrators about SSRF risks and secure coding practices to prevent similar vulnerabilities in the future.