Overview
CVE-2025-65018 is a high-severity heap buffer overflow vulnerability affecting libpng, the reference library for handling PNG (Portable Network Graphics) images. The vulnerability resides within the simplified API function png_image_finish_read and occurs during the processing of 16-bit interlaced PNG images when configured for 8-bit output format. Specifically, attacker-crafted interlaced PNG files can trigger heap writes beyond the allocated buffer bounds, potentially leading to arbitrary code execution or denial-of-service.
This vulnerability affects libpng versions 1.6.0 up to, but not including, 1.6.51. The issue has been addressed in libpng version 1.6.51.
Technical Details
The vulnerability stems from insufficient bounds checking within the png_image_finish_read function when handling interlaced PNG images. Interlacing involves storing an image in multiple passes, improving perceived rendering speed. The flawed logic allows malformed interlaced PNGs to cause the function to write data outside the boundaries of the allocated heap buffer. This write operation overwrites adjacent memory, which could lead to crashes, unexpected program behavior, or, in more sophisticated attacks, arbitrary code execution. The simplified API, intended for ease of use, inadvertently exposes this vulnerability when processing specific PNG configurations. The vulnerability exists when reading 16-bit PNG images while outputting to an 8-bit format due to incorrect calculations during interlaced processing.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns CVE-2025-65018 a score of 7.1, classifying it as HIGH severity.
- CVSS Score: 7.1
- Vector: (Detailed CVSS vector string would be here if available)
- Severity: HIGH
This score reflects the potential for remote code execution and the relatively low attack complexity associated with exploiting the vulnerability.
Possible Impact
Successful exploitation of CVE-2025-65018 can have significant consequences:
- Denial of Service (DoS): A malicious PNG image could crash the application processing it, leading to service unavailability.
- Arbitrary Code Execution: In the most severe scenario, an attacker could leverage the heap overflow to inject and execute arbitrary code on the affected system. This could allow the attacker to gain complete control of the system.
- Data Corruption: Overwriting memory outside the intended buffer can corrupt data, leading to application instability or incorrect results.
Applications that automatically process PNG images, such as web browsers, image viewers, and server-side image processing services, are particularly vulnerable.
Mitigation and Patch Steps
The most effective way to mitigate CVE-2025-65018 is to upgrade libpng to version 1.6.51 or later. This version contains the necessary patches to address the heap buffer overflow vulnerability.
- Upgrade libpng: Update to libpng version 1.6.51 or a later version.
- Recompile Applications: After upgrading libpng, recompile all applications that use the library to ensure they are linked against the patched version.
- Vendor Patches: Check for and apply any vendor-specific patches that include the updated libpng library.
- Web Application Firewalls (WAFs): While not a direct solution, WAFs can be configured to filter potentially malicious PNG images based on known attack patterns.
