CVE-2026-20345 in ClamAV
Summary
by MITRE • 08/07/2026
A vulnerability in the GPT file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition or possibly other expanded impacts as a result of memory corruption on an affected device.
This vulnerability is due to improper handling of an endian conversion operation, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted GPT file to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.
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Analysis
by VulDB Data Team • 08/07/2026
The vulnerability under examination resides within the Generic Partition Table (GPT) file format parser implementation of ClamAV, representing a critical security flaw that exposes systems to remote exploitation without authentication requirements. This weakness manifests through inadequate validation of endian conversion operations during file parsing processes, creating conditions where maliciously crafted GPT files can trigger memory corruption behaviors. The vulnerability operates at the intersection of file format parsing and memory safety, making it particularly dangerous as it can be exploited through routine scanning operations that occur when ClamAV processes potentially malicious files.
The technical mechanism behind this vulnerability involves improper handling of byte order conversions within the GPT structure parsing logic, specifically when processing partition entry arrays that contain metadata about disk partitions. When ClamAV encounters a malformed GPT file with manipulated endian values, the parser fails to properly validate array bounds before performing memory operations, leading to out-of-bounds buffer writes that corrupt adjacent memory regions. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and more specifically relates to CWE-787, concerning out-of-bounds write operations that can result in arbitrary code execution or system instability. The flaw demonstrates characteristics consistent with ATT&CK technique T1059.007, where adversaries manipulate system processes through file format exploitation.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more sophisticated attack vectors depending on the target environment and system configuration. When exploited successfully, the vulnerability forces ClamAV scanning processes to terminate abruptly, causing disruption to security operations and potentially allowing attackers to bypass detection mechanisms during critical system maintenance windows. The remote exploitation capability means that attackers can trigger this condition without physical access or authentication credentials, making it particularly dangerous in networked environments where ClamAV systems are deployed across multiple endpoints. The vulnerability affects systems where ClamAV is actively scanning files, including email servers, file sharing systems, and endpoint protection platforms, potentially creating cascading failures when security scanning becomes unavailable.
Mitigation strategies should prioritize immediate deployment of updated ClamAV versions that address the endian conversion handling issues in GPT parsing logic, following standard patch management protocols to minimize exposure windows. Organizations should implement network segmentation and monitoring to detect abnormal scanning behavior or process termination patterns that might indicate exploitation attempts, while also considering temporary disabling of GPT file scanning capabilities until proper patches are deployed. Security teams must establish baseline configurations that limit the scope of potentially vulnerable file types processed by ClamAV, implementing additional validation layers for suspicious file formats and establishing incident response procedures specifically designed to handle cases where security scanning systems themselves become compromised or unavailable through exploitation of parsing vulnerabilities.