CVE-2025-6660 is a high-severity heap-based buffer overflow vulnerability (CWE-122) found in PDF-XChange Editor version 10.5.2.395. The flaw arises during the parsing of GIF files embedded or linked within PDF documents. Specifically, the vulnerability is due to insufficient validation of the length of user-supplied data before copying it into a fixed-length buffer allocated on the heap. This improper bounds checking allows an attacker to overflow the buffer, potentially overwriting adjacent memory. Exploiting this vulnerability enables remote code execution (RCE) in the context of the current user process. However, exploitation requires user interaction, such as opening a malicious PDF file or visiting a webpage containing a crafted PDF with a malicious GIF image. The vulnerability does not require prior authentication or elevated privileges, making it accessible to remote attackers who can trick users into opening malicious content. The CVSS v3.0 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity but requiring user interaction. No known exploits are currently reported in the wild, but the presence of a reliable heap overflow in a widely used PDF editor poses a significant risk, especially in environments where PDF-XChange Editor is used extensively. The vulnerability was reported by the Zero Day Initiative (ZDI) and is publicly disclosed as of June 25, 2025. No patches or updates are currently linked, indicating that affected organizations must prioritize mitigation and monitoring until a vendor fix is released.

For European organizations, the impact of this vulnerability can be substantial. PDF-XChange Editor is a popular PDF viewer and editor used across various sectors including government, finance, legal, and education. Successful exploitation could allow attackers to execute arbitrary code, leading to full system compromise, data theft, or disruption of critical services. Confidential information could be exfiltrated or manipulated, and malware or ransomware could be deployed. Since the vulnerability requires user interaction, phishing campaigns or malicious document distribution are likely attack vectors. Organizations with high document exchange volumes or those relying on PDF workflows are particularly at risk. Additionally, sectors with stringent data protection requirements under GDPR could face compliance violations and reputational damage if breaches occur. The lack of an immediate patch increases the window of exposure, emphasizing the need for proactive defense. The vulnerability also poses a risk to endpoint security, potentially bypassing traditional antivirus or sandboxing solutions if the exploit is crafted to evade detection.

1. Immediate mitigation should include disabling or restricting the use of PDF-XChange Editor version 10.5.2.395, especially for users who frequently handle untrusted PDF files. 2. Employ application whitelisting and restrict execution privileges to limit the impact of potential code execution. 3. Implement strict email filtering and attachment scanning to detect and block malicious PDFs containing crafted GIF images. 4. Educate users on the risks of opening unsolicited or suspicious PDF documents and links, emphasizing the need for caution with email attachments. 5. Use endpoint detection and response (EDR) tools to monitor for anomalous behaviors indicative of exploitation attempts, such as unusual memory operations or process injections related to PDF-XChange Editor. 6. Until a vendor patch is available, consider sandboxing PDF-XChange Editor processes or running them with reduced privileges to contain potential exploits. 7. Regularly review and update intrusion detection/prevention system (IDS/IPS) signatures to include heuristics for this vulnerability once available. 8. Maintain comprehensive backups and incident response plans to quickly recover from potential compromises. 9. Monitor vendor communications and threat intelligence feeds for patch releases or exploit disclosures to promptly apply updates.