CVE-2007-1777 in PHP
Summary
by MITRE
Integer overflow in the zip_read_entry function in PHP 4 before 4.4.5 allows remote attackers to execute arbitrary code via a ZIP archive that contains an entry with a length value of 0xffffffff, which is incremented before use in an emalloc call, triggering a heap overflow.
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Analysis
by VulDB Data Team • 04/19/2025
The vulnerability identified as CVE-2007-1777 represents a critical integer overflow flaw within PHP's zip extension that existed in versions prior to 4.4.5. This vulnerability specifically affects the zip_read_entry function which processes ZIP archive entries during decompression operations. The flaw occurs when the system encounters a ZIP entry with a length value of 0xffffffff, which when processed through the emalloc memory allocation function, causes an integer overflow condition that can be exploited for remote code execution. This issue falls under the CWE-190 category of Integer Overflow or Wraparound, a well-documented vulnerability pattern that occurs when an integer operation exceeds the maximum value that can be represented by the integer type.
The technical exploitation of this vulnerability begins with a remote attacker crafting a malicious ZIP archive containing an entry with the maximum 32-bit unsigned integer value of 0xffffffff. When PHP's zip extension processes this archive, the zip_read_entry function attempts to read this entry and increment the length value before passing it to the emalloc memory allocation function. Due to the integer overflow, the incremented value wraps around to a very small positive integer or zero, but the subsequent memory allocation attempt uses this corrupted value to request memory from the heap. This heap-based memory corruption creates opportunities for attackers to manipulate memory layout and potentially execute arbitrary code with the privileges of the web server process.
The operational impact of this vulnerability extends beyond simple remote code execution as it can be leveraged in various attack scenarios including web server compromise, privilege escalation, and persistent backdoor establishment. Attackers can exploit this vulnerability by uploading malicious ZIP files to web applications that process user-uploaded content, or by directly targeting PHP applications that handle ZIP archive decompression. The vulnerability is particularly dangerous because it requires no special privileges to exploit and can be triggered through normal web application functionality. According to ATT&CK framework, this vulnerability maps to T1059.007 (Command and Scripting Interpreter: PowerShell) and T1190 (Exploit Public-Facing Application) techniques, as it allows for exploitation of web applications through the ZIP archive processing functionality.
The mitigation strategy for this vulnerability requires immediate patching of all affected PHP installations to version 4.4.5 or later, where the integer overflow has been corrected through proper input validation and boundary checking. System administrators should also implement additional security controls such as restricting file upload capabilities, implementing proper input sanitization for ZIP archive processing, and monitoring for unusual file upload patterns. Organizations should also consider implementing web application firewalls and intrusion detection systems to detect and prevent exploitation attempts. The fix implemented in PHP 4.4.5 addresses the root cause by adding proper validation of entry lengths and preventing the integer overflow condition before it can be used in memory allocation operations. This vulnerability highlights the importance of proper integer handling in memory management functions and demonstrates how seemingly simple flaws in input validation can lead to severe security consequences.