CVE-2025-27931 is an out-of-bounds read vulnerability identified in the EMF (Enhanced Metafile) processing functionality of PDF-XChange Editor version 10.5.2.395, a widely used PDF viewing and editing software developed by PDF-XChange Co. Ltd. The vulnerability arises when the software processes a specially crafted EMF file embedded or linked within a PDF document. An out-of-bounds read occurs when the software attempts to read memory outside the allocated buffer boundaries, which can lead to the disclosure of sensitive information stored in adjacent memory regions. This vulnerability is classified under CWE-125, indicating improper bounds checking during memory read operations. Exploitation requires an attacker to deliver a malicious PDF containing the crafted EMF file to the victim, who must then open or preview the file in the vulnerable version of PDF-XChange Editor. The CVSS v3.1 base score is 6.5, reflecting a medium severity level, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), high confidentiality impact (C:H), no integrity impact (I:N), and no availability impact (A:N). No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability primarily threatens confidentiality by potentially leaking sensitive data from the application's memory space during EMF file parsing.

For European organizations, this vulnerability poses a risk of sensitive information leakage, particularly in sectors where PDF-XChange Editor is used extensively for document handling, such as legal, financial, healthcare, and government institutions. Confidential data could be exposed if an attacker successfully convinces a user to open a malicious PDF containing the crafted EMF file. Although the vulnerability does not affect integrity or availability, the confidentiality breach could lead to data privacy violations under regulations like GDPR, resulting in legal and financial repercussions. The requirement for user interaction (opening the malicious file) limits automated exploitation but does not eliminate risk, especially in environments with high document exchange volumes or targeted spear-phishing campaigns. The absence of known exploits in the wild suggests limited immediate threat, but the medium severity score and potential for sensitive data exposure warrant proactive mitigation.

European organizations should implement the following specific measures: 1) Immediately identify and inventory all instances of PDF-XChange Editor version 10.5.2.395 in use across the enterprise. 2) Restrict or disable the automatic preview of PDF files in email clients or document management systems to reduce the risk of inadvertent triggering of the vulnerability. 3) Educate users on the risks of opening unsolicited or unexpected PDF attachments, emphasizing caution with files from unknown or untrusted sources. 4) Monitor for updates or patches from PDF-XChange Co. Ltd and apply them promptly once available. 5) Employ network-level defenses such as sandboxing or advanced threat protection solutions that can analyze and block malicious PDFs before reaching end users. 6) Consider deploying application whitelisting or restricting the use of vulnerable versions of PDF-XChange Editor, replacing them with alternative PDF readers with a better security posture if patching is delayed. 7) Implement Data Loss Prevention (DLP) controls to detect and prevent unauthorized exfiltration of sensitive information that could result from exploitation.