CVE-2025-20260: Buffer Overflow Vulnerability in ClamAV’s PDF Scanning Process

Overview

In the ever-evolving landscape of cybersecurity, vulnerabilities are often discovered that can potentially compromise system security or result in data leakage. One such vulnerability, identified as CVE-2025-20260, has been detected in the PDF scanning processes of ClamAV, a popular open-source antivirus engine. This vulnerability affects any system or device that utilizes the ClamAV engine for scanning PDF files. The matter is of utmost importance as it might allow an unauthenticated, remote attacker to cause a buffer overflow condition, leading to a denial of service (DoS) or potentially executing arbitrary code on the affected device.

Vulnerability Summary

CVE ID: CVE-2025-20260
Severity: Critical (CVSS: 9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Buffer overflow potentially leading to a denial of service condition or execution of arbitrary code on the affected system.

Affected Products

Product | Affected Versions

ClamAV | All versions up to the latest release

How the Exploit Works

The vulnerability arises due to incorrect memory buffer allocation when ClamAV processes PDF files. An attacker can exploit this vulnerability by crafting a malicious PDF file and submitting it to be scanned by ClamAV on the affected device. If successful, this could trigger a buffer overflow condition, likely resulting in the termination of the ClamAV scanning process and a DoS condition on the affected software. Although not yet proven, it is also possible that an attacker could leverage this buffer overflow to execute arbitrary code with the privileges of the ClamAV process.

Conceptual Example Code

Here’s a conceptual example of how this vulnerability might be exploited. This pseudocode represents a maliciously crafted PDF file:

# Pseudocode representing a malicious PDF
class MaliciousPDF:
def __init__(self):
self.payload = "A"*5000  # Overflows the buffer
malicious_pdf = MaliciousPDF()
ClamAV.scan(malicious_pdf)  # Triggers buffer overflow

In the above example, the payload is an extremely large string designed to overflow the buffer when scanned by ClamAV.

Recommendations

The recommended mitigation for this vulnerability is to apply the patch provided by the vendor as soon as it is available. As a temporary countermesure, you can use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to identify and block potential attacks. Users are also advised to avoid scanning unsolicited PDF files and to only scan files from trusted sources.
Stay tuned for more updates on this and other cybersecurity vulnerabilities. Protecting your systems and data is our top priority.