CVE-2007-2445 in libpng
Summary
by MITRE
The png_handle_tRNS function in pngrutil.c in libpng before 1.0.25 and 1.2.x before 1.2.17 allows remote attackers to cause a denial of service (application crash) via a grayscale PNG image with a bad tRNS chunk CRC value.
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Analysis
by VulDB Data Team • 01/13/2025
The vulnerability described in CVE-2007-2445 represents a critical denial of service flaw affecting the libpng library version 1.0.25 and earlier, as well as 1.2.x versions prior to 1.2.17. This issue specifically targets the png_handle_tRNS function within the pngrutil.c source file, which processes transparency information in PNG images through the tRNS chunk. The vulnerability arises when processing grayscale PNG images containing malformed tRNS chunks with invalid cyclic redundancy check values, creating a scenario where legitimate image processing operations can be disrupted through crafted input data.
The technical flaw manifests in the improper handling of checksum validation during PNG chunk processing. When a grayscale PNG image contains a tRNS chunk with an incorrect CRC value, the png_handle_tRNS function fails to properly validate the chunk data before attempting to process it, leading to memory corruption or invalid memory access patterns. This behavior directly maps to CWE-125, which describes out-of-bounds read vulnerabilities, and CWE-248, which covers unspecified other runtime errors. The function's failure to implement proper error handling for malformed chunks results in application termination rather than graceful error recovery, making it susceptible to exploitation by remote attackers who can craft malicious PNG files.
The operational impact of this vulnerability extends beyond simple service disruption, as it affects any application relying on libpng for image processing, including web servers, image editing software, and content management systems. Attackers can exploit this weakness by uploading or serving specially crafted grayscale PNG images that trigger the vulnerable code path, causing applications to crash and potentially leading to complete service unavailability. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through application-level manipulation, and represents a classic example of how input validation failures can be leveraged for denial of service attacks in widely deployed software libraries.
Mitigation strategies for this vulnerability require immediate patching of affected libpng versions to either 1.0.25 or 1.2.17 and later releases, which contain proper error handling for malformed tRNS chunks. Organizations should also implement input validation measures at the application level to verify PNG file integrity before processing, though this approach remains secondary to the core library fix. Additionally, network-level protections such as content filtering and rate limiting can help reduce the impact of exploitation attempts, while monitoring systems should be configured to detect application crashes or restart patterns that may indicate successful exploitation attempts against this vulnerability.