CVE-2007-4577 in Sophos
Summary
by MITRE
Sophos Anti-Virus for Unix/Linux before 2.48.0 allows remote attackers to cause a denial of service (infinite loop) via a malformed BZip file that results in the creation of multiple Engine temporary files (aka a "BZip bomb").
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability described in CVE-2007-4577 represents a critical denial of service weakness in Sophos Anti-Virus for Unix/Linux versions prior to 2.48.0. This flaw specifically targets the BZip compression handling mechanism within the antivirus software, creating a scenario where maliciously crafted BZip files can trigger an infinite loop condition. The vulnerability stems from inadequate input validation and processing logic that fails to properly handle malformed BZip archives, leading to resource exhaustion and system instability.
The technical implementation of this vulnerability involves the creation of multiple Engine temporary files when processing malformed BZip archives, which results in an infinite loop during decompression operations. Attackers can exploit this by crafting specially designed BZip files that cause the antivirus engine to continuously create temporary files without proper termination conditions. This behavior directly violates the principle of resource management and proper input sanitization that should be implemented in security software to prevent such exploitation scenarios. The flaw operates at the file processing level where the BZip decompression routine fails to implement adequate loop detection and resource limitation mechanisms.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and performance. When exploited, the infinite loop causes continuous resource consumption, leading to system slowdowns, potential system crashes, and denial of service conditions for legitimate users. The creation of multiple temporary files can quickly exhaust available disk space, while the continuous loop consumes CPU cycles and memory resources. This vulnerability is particularly dangerous in server environments where continuous availability is critical, as it can be exploited remotely without requiring authentication or elevated privileges, making it an attractive target for attackers seeking to disrupt services.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability, beginning with immediate patching to Sophos Anti-Virus for Unix/Linux versions 2.48.0 and later. The fix typically involves implementing proper input validation for BZip files, adding resource limits to prevent excessive temporary file creation, and incorporating loop detection mechanisms within the decompression routines. Organizations should also consider implementing network-level filtering to prevent suspicious BZip files from reaching the antivirus engines, utilizing techniques such as file type validation and size restrictions. From a compliance perspective, this vulnerability aligns with CWE-400, which addresses improper resource management, and relates to ATT&CK technique T1499.004 for network denial of service. Additionally, the vulnerability demonstrates the importance of proper input sanitization and resource management practices in security software, as outlined in various cybersecurity frameworks and standards including NIST SP 800-53 and ISO 27001 controls.