The vulnerability identified as CVE-2025-68431 affects the libheif library, which is widely used for decoding and encoding HEIF and AVIF image formats. The flaw lies in the HeifPixelImage::overlay() function, which handles overlay image items within HEIF files. When a specially crafted HEIF file exercises the overlay image item path, the function calculates a row length that can become negative due to an unclipped overlay rectangle or invalid offset values. This negative value is then cast to an unsigned size_t type, causing an integer underflow that results in a very large size passed to memcpy. Consequently, the memcpy operation reads beyond the allocated source buffer, leading to a heap buffer over-read and application crash. This vulnerability does not compromise confidentiality or integrity but impacts availability by causing denial of service. The vulnerability requires no privileges but does require user interaction to trigger, such as opening or processing a malicious HEIF image. The issue was addressed in libheif version 1.21.0 by correcting the bounds checking and overlay rectangle validation. No public exploits have been reported, but the nature of the vulnerability suggests potential for denial of service attacks if exploited. The workaround involves avoiding decoding images that include 'iovl' overlay boxes, which are the vector for triggering the vulnerability.

For European organizations, the primary impact of CVE-2025-68431 is the risk of denial of service in applications or services that utilize libheif for image decoding. This includes media processing platforms, content management systems, digital asset management solutions, and any software handling HEIF or AVIF images. A successful exploit could cause application crashes, service interruptions, or system instability, potentially disrupting business operations or user experience. While no direct data breach or code execution is indicated, denial of service can affect availability of critical services, especially in sectors relying heavily on multimedia content such as media companies, digital marketing agencies, and software vendors. Additionally, embedded systems or IoT devices using libheif for image processing could be impacted, leading to device malfunctions. The requirement for user interaction limits remote exploitation but does not eliminate risk, as malicious images could be delivered via email, websites, or file sharing. Organizations processing large volumes of user-generated content or third-party images are particularly at risk.

European organizations should immediately upgrade libheif to version 1.21.0 or later to apply the official patch that fixes the vulnerability. Where upgrading is not immediately feasible, implement strict input validation and filtering to block or quarantine HEIF images containing overlay ('iovl') boxes. Employ sandboxing or isolated environments for image processing tasks to contain potential crashes and prevent broader system impact. Update antivirus and endpoint protection solutions to detect malformed HEIF files exploiting this vulnerability. Educate users and administrators about the risks of opening untrusted HEIF images, especially those received via email or downloaded from unverified sources. Monitor application logs for crashes related to image decoding and investigate suspicious image files. For embedded or IoT devices using libheif, coordinate with vendors for firmware updates or apply mitigations to restrict image input sources. Finally, integrate this vulnerability into incident response plans to quickly address any exploitation attempts.