CVE-2025-70559 is a security vulnerability found in the pdfminer.six Python library, specifically in versions prior to 20251230. The vulnerability is due to insecure deserialization in the CMap loading mechanism, where the library uses Python's pickle module to deserialize CMap cache files without validating their integrity or origin. Pickle is known to be unsafe when handling untrusted data because it can instantiate arbitrary Python objects, potentially leading to arbitrary code execution. An attacker who can place a maliciously crafted pickle file in a location accessible to the application can trigger this vulnerability when the trusted process loads the file. This can result in arbitrary code execution or privilege escalation. The root cause is an incomplete patch addressing a previous vulnerability, CVE-2025-64512, indicating that the fix did not fully address the insecure deserialization risk. The vulnerability requires that the attacker have the capability to write files to the target system in locations where the application loads CMap cache files, which may be possible in multi-user or shared environments or through other vulnerabilities. There are no known public exploits at this time, but the risk remains significant due to the nature of pickle deserialization. The vulnerability affects any system using vulnerable versions of pdfminer.six, which is commonly used in Python applications for PDF parsing and analysis. This can impact automated document processing pipelines, malware analysis tools, or any service that processes PDF files using this library. The lack of a CVSS score suggests that the vulnerability is newly published and not yet fully assessed. However, the potential for arbitrary code execution and privilege escalation without user interaction but requiring file placement indicates a high severity level.

For European organizations, the impact of CVE-2025-70559 can be substantial, especially for those relying on pdfminer.six for PDF parsing in automated workflows, document management systems, or security tools. Successful exploitation could allow attackers to execute arbitrary code within the context of the vulnerable application, potentially leading to full system compromise or privilege escalation. This could result in data breaches, disruption of critical services, or lateral movement within networks. Organizations processing untrusted PDF files or operating in multi-tenant environments are at higher risk, as attackers may leverage this vulnerability to implant malicious payloads. The vulnerability could also be exploited to bypass security controls if the compromised application has elevated privileges or access to sensitive data. Given the widespread use of Python in European IT environments and the popularity of pdfminer.six for PDF processing, the threat could affect a broad range of sectors including finance, government, healthcare, and technology. The absence of known exploits currently provides a window for proactive mitigation, but the incomplete patch history suggests attackers may develop exploits soon.

To mitigate CVE-2025-70559, organizations should: 1) Update pdfminer.six to the fixed version released after 20251230 as soon as it becomes available, ensuring the insecure deserialization flaw is fully patched. 2) Restrict file system permissions to prevent unauthorized users or processes from writing to directories where CMap cache files are loaded, minimizing the risk of malicious file placement. 3) Implement application-level validation or sandboxing of deserialization operations to detect or block untrusted pickle files. 4) Employ runtime monitoring and intrusion detection to identify anomalous behavior indicative of exploitation attempts. 5) Review and harden the environment where pdfminer.six is used, including containerization or running processes with least privilege. 6) Educate developers and administrators about the risks of insecure deserialization and the dangers of using pickle with untrusted data. 7) Consider alternative PDF parsing libraries that do not rely on insecure deserialization if immediate patching is not feasible. 8) Conduct regular security audits and penetration testing focusing on file handling and deserialization components.