CVE-2016-4342 in PHP
Summary
by MITRE
ext/phar/phar_object.c in PHP before 5.5.32, 5.6.x before 5.6.18, and 7.x before 7.0.3 mishandles zero-length uncompressed data, which allows remote attackers to cause a denial of service (heap memory corruption) or possibly have unspecified other impact via a crafted (1) TAR, (2) ZIP, or (3) PHAR archive.
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Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-4342 represents a critical heap memory corruption issue affecting PHP versions prior to specific patch releases. This flaw exists within the phar_object.c file in the ext/phar extension, which is responsible for handling phar archives in PHP applications. The vulnerability specifically manifests when processing zero-length uncompressed data within archive files, creating a condition where maliciously crafted archive files can trigger unpredictable behavior in the PHP runtime environment.
The technical exploitation of this vulnerability occurs through the manipulation of archive formats including TAR, ZIP, and PHAR archives that contain zero-length uncompressed data segments. When PHP attempts to parse these malformed archives, the phar extension fails to properly handle the edge case of zero-length data blocks, leading to heap memory corruption. This memory corruption can result in application crashes, denial of service conditions, or potentially more severe consequences depending on the execution context. The vulnerability is particularly dangerous because it can be triggered remotely through user-supplied archive files that are processed by PHP applications without proper validation.
From an operational impact perspective, this vulnerability poses significant risks to web applications that process user-uploaded archives or rely on PHP's phar extension for archive handling. Attackers can craft malicious archives that, when processed by vulnerable PHP applications, will cause the web server to consume excessive memory or crash entirely, leading to denial of service for legitimate users. The potential for unspecified other impacts suggests that under certain conditions, this memory corruption could potentially be exploited for more advanced attacks, though the primary concern remains the reliability and availability of affected systems. The vulnerability affects multiple PHP version lines, making it widespread across many production environments that had not yet applied the relevant security patches.
Organizations should prioritize immediate patching of all affected PHP installations to mitigate this vulnerability. The recommended remediation involves upgrading to PHP versions 5.5.32, 5.6.18, or 7.0.3 respectively, depending on the current PHP version in use. Additionally, implementing proper input validation and sanitization for all archive file processing, along with restricting archive file uploads to trusted sources, can provide defense-in-depth measures. Security monitoring should include detection of suspicious archive file patterns and unusual memory consumption patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a significant concern for compliance with security standards such as those outlined in the OWASP Top Ten and NIST cybersecurity frameworks. The ATT&CK framework categorizes this as a denial of service attack vector that could potentially be leveraged for further compromise if combined with other attack techniques.