CVE-2017-11147 in PHP
Summary
by MITRE
In PHP before 5.6.30 and 7.x before 7.0.15, the PHAR archive handler could be used by attackers supplying malicious archive files to crash the PHP interpreter or potentially disclose information due to a buffer over-read in the phar_parse_pharfile function in ext/phar/phar.c.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-11147 represents a critical buffer over-read flaw in PHP's PHAR archive handling mechanism that affects versions prior to 5.6.30 and 7.0.15. This vulnerability resides within the phar_parse_pharfile function located in the ext/phar/phar.c source file, where improper input validation leads to memory access violations. The flaw specifically manifests when PHP processes maliciously crafted PHAR archive files, creating potential attack vectors that could be exploited by remote adversaries to compromise system integrity.
The technical nature of this vulnerability stems from insufficient bounds checking during the parsing of PHAR archive metadata, particularly in how the parser handles compressed data structures. When a malformed PHAR file is processed, the phar_parse_pharfile function attempts to read beyond allocated memory buffers, resulting in undefined behavior that can manifest as interpreter crashes or information disclosure. This buffer over-read condition creates a pathway for attackers to potentially extract sensitive data from memory regions adjacent to the affected buffers, as the parser fails to properly validate the size and structure of archive components.
The operational impact of CVE-2017-11147 extends beyond simple denial of service scenarios, as the vulnerability presents potential information disclosure risks that could expose system memory contents to attackers. The crash conditions can be leveraged to cause application instability and service disruption, while the information disclosure aspect may reveal sensitive data such as stack contents, heap metadata, or other memory segments that could aid in further exploitation attempts. This vulnerability directly affects web applications that utilize PHAR archives for file handling, deployment, or data processing operations, particularly those running on affected PHP versions.
Security practitioners should recognize this vulnerability as mapping to CWE-125: Out-of-bounds Read, which is categorized under the broader class of memory safety issues in software development. The vulnerability aligns with ATT&CK technique T1059.007: Command and Scripting Interpreter: PowerShell, though in this case the attack vector involves PHAR archive manipulation rather than PowerShell execution. Organizations should prioritize immediate patching of affected PHP installations, as the vulnerability can be exploited remotely through web applications that accept user-supplied PHAR files without proper validation. Additionally, implementing proper input sanitization and file type validation mechanisms can help reduce the attack surface while awaiting patch deployment.
The remediation strategy should focus on upgrading to PHP versions 5.6.30 or later, and 7.0.15 or later, where the buffer over-read has been addressed through proper bounds checking implementation. Security configurations should include disabling PHAR archive processing for untrusted inputs and implementing strict file validation procedures. Network segmentation and monitoring for suspicious PHAR file handling activities can provide additional defense-in-depth measures. Organizations should also conduct thorough vulnerability assessments to identify all systems running affected PHP versions and ensure comprehensive patch management processes are in place to prevent similar vulnerabilities from persisting in their environments.