pdfminer.six Insecure Deserialization Vulnerability in CMap Loader Leading to Privilege Escalation

A vulnerability allowing insecure deserialization has been identified in pdfminer.six versions prior to 20251230. This issue arises in the CMap loading mechanism, where the library uses Python's pickle module to deserialize CMap cache files without proper validation. An attacker who can place a malicious pickle file in a directory accessible to the application can exploit this vulnerability, potentially leading to arbitrary code execution or unauthorized privilege escalation. This flaw is particularly concerning in multi-user or server environments, where a low-privileged user could gain root access or escalate to a service account by exploiting the deserialization vulnerability.

Impact

Exploitation of this vulnerability allows for arbitrary code execution with the privileges of the user running pdfminer, which could be root or a privileged service account. This could lead to unauthorized access, modification of system files, or other malicious activities under the guise of a trusted user.

Reproduction

The vulnerability can be reproduced by creating a malicious CMap file in a directory that is writable by the user. This directory must be included in the CMap search path. Once the malicious file is placed, a privileged user can load the CMap file, triggering the deserialization of the malicious pickle file and executing arbitrary code with elevated privileges.

Remediation

Users are advised to update to pdfminer.six version 20251230 or later, where this vulnerability has been addressed.