CVE-2011-1471 in PHP
Summary
by MITRE • 01/25/2023
Integer signedness error in zip_stream.c in the Zip extension in PHP before 5.3.6 allows context-dependent attackers to cause a denial of service (CPU consumption) via a malformed archive file that triggers errors in zip_fread function calls.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2011-1471 represents a critical integer signedness error within the Zip extension of PHP versions prior to 5.3.6. This flaw exists in the zip_stream.c file and specifically impacts the zip_fread function calls when processing malformed archive files. The vulnerability classifies under CWE-190 as an integer overflow/underflow condition, where the improper handling of signed and unsigned integer operations creates a scenario for malicious exploitation.
The technical implementation of this vulnerability stems from how PHP's Zip extension processes archive files during decompression operations. When a malformed zip archive is encountered, the zip_fread function encounters an integer signedness error that causes it to enter an infinite loop or consume excessive CPU resources. This occurs because the extension fails to properly validate the signedness of integer values used in file read operations, particularly when dealing with archive metadata such as file sizes, offsets, or compression parameters. The error manifests when the system attempts to read data from the archive using improperly calculated buffer sizes or read lengths that result in negative or unexpectedly large integer values.
The operational impact of this vulnerability extends beyond simple denial of service, creating significant security implications for web applications that process user-uploaded zip files. Attackers can exploit this weakness by crafting malicious zip archives that trigger the integer signedness error, causing web servers to consume excessive CPU cycles and potentially leading to complete service unavailability. This makes the vulnerability particularly dangerous in environments where PHP applications handle untrusted zip file uploads, such as content management systems, file sharing platforms, or any application that allows users to upload and process compressed archives. The resource exhaustion can be sustained over time, making it difficult to distinguish from legitimate high-usage patterns and potentially allowing for prolonged system degradation.
Organizations affected by this vulnerability should implement immediate mitigation strategies including upgrading to PHP version 5.3.6 or later where the fix has been implemented. The patch addresses the root cause by ensuring proper validation of integer values during zip file processing and implementing bounds checking mechanisms that prevent the signedness error from occurring. Additionally, administrators should deploy input validation controls at multiple layers including web application firewalls, file type restrictions, and resource monitoring systems to detect and prevent exploitation attempts. This vulnerability aligns with ATT&CK technique T1499.004 for resource exhaustion and demonstrates the importance of proper integer handling in security-critical code paths. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates across all affected systems and applications that utilize PHP's Zip extension functionality.