CVE-2024-25676 is a medium-severity vulnerability identified in ViewerJS version 0.5.8. The issue arises from improper sanitization of URLs loaded via URL TAGs within the component's script. This flaw enables two primary attack vectors: open redirection and out-of-band (OOB) resource loading. Open redirection vulnerabilities allow attackers to redirect users to malicious external sites by manipulating URL parameters, potentially facilitating phishing attacks or bypassing security controls. The out-of-band resource loading aspect means that the vulnerable component can be tricked into fetching resources from attacker-controlled servers, which can be leveraged for information leakage, server-side request forgery (SSRF), or to trigger side effects on external systems. The CVSS 3.1 base score of 4.7 reflects a medium severity, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is changed (S:C), indicating that exploitation affects components beyond the vulnerable one. The impact is limited to integrity (I:L) with no confidentiality or availability impact. No known exploits are reported in the wild, and no patches have been linked yet. The vulnerability is classified under CWE-601, which corresponds to open redirect issues. ViewerJS is an open-source web-based document viewer that renders PDFs and other documents in browsers without plugins, often embedded in web applications or intranet portals. The vulnerability could be exploited by attackers to redirect users to malicious sites or cause unintended external resource loads, potentially leading to phishing, tracking, or SSRF-related attacks.

For European organizations, the impact of CVE-2024-25676 depends on the extent to which ViewerJS is integrated into their web applications or internal portals. Organizations using ViewerJS to display documents to employees, customers, or partners may inadvertently expose users to phishing risks via open redirects, undermining user trust and potentially leading to credential theft or malware infections. The out-of-band resource loading could be exploited to perform SSRF attacks, which might allow attackers to probe internal networks or exfiltrate data indirectly. Although the vulnerability does not directly compromise confidentiality or availability, the integrity impact and user redirection risks can facilitate broader social engineering or lateral attack chains. Given the medium severity and requirement for user interaction, the threat is moderate but should not be overlooked, especially in sectors with high regulatory requirements such as finance, healthcare, and government. Additionally, organizations with strict data protection obligations under GDPR must consider the reputational and compliance risks associated with phishing or SSRF incidents stemming from this vulnerability.

1. Immediate mitigation involves auditing all web applications and portals for the presence of ViewerJS 0.5.8 or earlier versions. 2. If ViewerJS is in use, restrict or sanitize all user-controllable URL parameters that influence content loading to prevent injection of malicious URLs. 3. Implement Content Security Policy (CSP) headers to restrict the domains from which resources can be loaded, thereby limiting the impact of out-of-band resource loading. 4. Employ URL validation and whitelist approaches to ensure only trusted URLs are processed by the ViewerJS component. 5. Educate users to recognize suspicious redirects and avoid clicking on unexpected links. 6. Monitor web server logs for unusual redirect patterns or external resource requests indicative of exploitation attempts. 7. Engage with the ViewerJS community or maintainers to track the release of official patches or updates addressing this vulnerability and plan prompt upgrades. 8. Where feasible, consider alternative document viewers with stronger security postures until a fix is available. 9. For internal applications, restrict access to trusted networks and implement network segmentation to reduce SSRF impact.