CVE-2025-4639 is a high-severity vulnerability classified under CWE-611, which pertains to Improper Restriction of XML External Entity (XXE) Reference. This vulnerability affects the Peergos product, specifically versions up to and including 1.1.0. The flaw exists in the getDocumentBuilder() method of the WebDav servlet component of Peergos. XXE vulnerabilities arise when XML parsers process external entity references without proper restrictions, allowing attackers to read arbitrary files, perform server-side request forgery (SSRF), or cause denial of service (DoS) conditions. In this case, the vulnerability allows an unauthenticated remote attacker to exploit the XML parser by sending crafted XML payloads to the WebDav servlet, which processes XML documents. The CVSS 4.0 base score of 8.8 reflects a network attack vector (AV:N), low attack complexity (AC:L), no privileges or user interaction required (PR:N/UI:N), and a high impact on confidentiality (VC:H), with no impact on integrity or availability. The scope is limited to the vulnerable component (SC:L), and there are no known exploits in the wild as of the publication date. The vulnerability could lead to unauthorized disclosure of sensitive information stored on the server or accessible via the server's file system, potentially exposing confidential user data or internal system files. Given that Peergos is a privacy-focused, decentralized file storage and sharing platform, exploitation could undermine the confidentiality guarantees of the system and erode user trust. The lack of authentication requirements and the network attack vector make this vulnerability particularly dangerous, as it can be exploited remotely without any credentials or user interaction. No official patches have been linked yet, indicating that users must be vigilant and consider temporary mitigations until an update is available.

For European organizations using Peergos, especially those handling sensitive or personal data under GDPR regulations, this vulnerability poses a significant risk. Exploitation could lead to unauthorized data disclosure, violating data protection laws and resulting in legal and financial penalties. Confidentiality breaches could affect organizations in sectors such as healthcare, finance, legal services, and government agencies that rely on Peergos for secure file sharing. The remote and unauthenticated nature of the exploit increases the attack surface, potentially allowing threat actors to target European entities without prior access. Additionally, the reputational damage from a data breach involving a privacy-centric platform could be severe, undermining trust in decentralized storage solutions. The vulnerability also raises concerns about compliance with European cybersecurity directives like NIS2, which emphasize the protection of critical infrastructure and essential services. Organizations may face operational disruptions if sensitive internal documents are exposed or manipulated indirectly through information disclosure. Overall, the impact is primarily on confidentiality, with potential cascading effects on regulatory compliance, operational security, and organizational reputation.

1. Immediate mitigation should include disabling or restricting access to the WebDav servlet in Peergos installations until a patch is released. This can be done by firewall rules or application-level access controls limiting connections to trusted networks or IP addresses. 2. Employ XML parser configuration hardening by disabling external entity processing and DTDs in the XML parser used by Peergos, if possible through configuration overrides or custom wrappers. 3. Monitor network traffic for unusual or malformed XML payloads targeting the WebDav endpoint, using intrusion detection systems (IDS) or web application firewalls (WAF) with custom rules to detect XXE attack patterns. 4. Conduct thorough code audits and penetration testing focusing on XML processing components to identify and remediate similar issues proactively. 5. Stay updated with Peergos vendor advisories and apply official patches promptly once available. 6. Implement network segmentation to isolate Peergos servers from critical internal systems to limit lateral movement in case of compromise. 7. Educate system administrators and security teams about the risks of XXE vulnerabilities and the importance of secure XML parsing practices. These steps go beyond generic advice by focusing on immediate access restrictions, parser hardening, and active monitoring tailored to the specific vulnerable component.