CVE-2021-27506 in Network Security
Summary
by MITRE • 03/19/2021
The ClamAV Engine (Version 0.103.1 and below) embedded in Storsmshield Network Security (1.0 to 4.1.5) is subject to DoS in case of parsing of malformed png files.
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Analysis
by VulDB Data Team • 08/20/2024
The vulnerability identified as CVE-2021-27506 represents a critical denial of service condition within the ClamAV engine version 0.103.1 and earlier, which is integrated into Storssmshield Network Security appliances running versions 1.0 through 4.1.5. This weakness stems from inadequate input validation mechanisms during the processing of portable network graphics file format parsing operations. The flaw specifically manifests when the ClamAV engine encounters malformed png files that trigger unexpected behavior in the parsing routines, leading to system instability and potential service disruption.
The technical implementation of this vulnerability resides in the engine's failure to properly sanitize and validate png file headers and data structures before attempting to parse them. When processing malformed png files, the ClamAV engine exhibits memory corruption patterns and execution flow disruptions that ultimately result in complete service termination. This behavior aligns with CWE-129, which addresses insufficient input validation, and more specifically relates to CWE-476, dealing with null pointer dereferences that commonly occur during malformed file processing. The vulnerability demonstrates characteristics consistent with attack patterns catalogued in the MITRE ATT&CK framework under the T1499.004 technique for network denial of service attacks.
The operational impact of this vulnerability extends beyond simple service interruption to encompass broader network security implications for organizations relying on Storssmshield appliances for threat detection. Network security operations may experience unexpected downtime during routine scanning operations when encountering maliciously crafted png files in email attachments, web traffic, or file transfers. The vulnerability affects the appliance's ability to maintain continuous protection services, potentially leaving networks exposed to other threats during the service disruption period. Organizations utilizing these appliances may face significant operational challenges including increased incident response times and potential compliance violations due to service unavailability.
Mitigation strategies for CVE-2021-27506 should prioritize immediate software updates to ClamAV engine versions 0.103.2 and later, which contain patches addressing the png parsing vulnerabilities. Network administrators should implement additional file validation layers and consider deploying network segmentation to limit the impact of potential exploitation. Organizations should also establish monitoring protocols to detect unusual scanning behavior or service interruptions that may indicate exploitation attempts. Security teams should conduct thorough vulnerability assessments of their network security infrastructure to identify all affected Storssmshield appliances and ensure comprehensive patch deployment across all systems. The remediation process should include testing procedures to validate that the patch resolves the vulnerability without introducing compatibility issues with existing network security policies and scanning configurations.