CVE-2023-39329 is a vulnerability identified in OpenJPEG version 2.5.0, an open-source JPEG 2000 codec widely used for image compression and decompression. The flaw resides in the opj_t1_decode_cblks function within the tcd.c source file, where improper handling of crafted JPEG 2000 image files can lead to uncontrolled resource consumption. Specifically, the vulnerability allows an attacker to trigger excessive CPU or memory usage during the decoding process, resulting in a denial of service (DoS) condition. This occurs because the function does not adequately limit or validate resource allocation when processing certain image data blocks, causing the system to exhaust available resources. The attack vector requires no privileges (network attack vector) but does require user interaction, such as opening or processing a malicious image file. The CVSS v3.1 base score is 6.5 (medium severity), reflecting the lack of impact on confidentiality or integrity but significant impact on availability. No known exploits have been reported in the wild, but the vulnerability poses a risk to any system that automatically processes untrusted JPEG 2000 images using the affected OpenJPEG version. Since OpenJPEG is embedded in various software products and services, the vulnerability could affect a broad range of applications, including document viewers, media processing pipelines, and web services handling image uploads.

For European organizations, this vulnerability primarily threatens service availability by enabling denial of service attacks through resource exhaustion. Organizations that rely on OpenJPEG 2.5.0 for image decoding in critical workflows—such as digital media companies, publishing houses, government document management systems, and healthcare imaging platforms—may experience service disruptions or degraded performance. This could lead to operational downtime, delayed processing, and potential loss of business continuity. Although the vulnerability does not compromise data confidentiality or integrity, the availability impact can indirectly affect user trust and operational efficiency. Additionally, automated systems that ingest images from external sources without proper validation are at higher risk. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits targeting this vulnerability. European organizations with stringent uptime requirements or those operating in sectors with critical imaging needs should prioritize mitigation to prevent potential denial of service incidents.

To mitigate CVE-2023-39329, European organizations should first verify if they use OpenJPEG version 2.5.0 in their software stack. If so, they should apply any available patches or updates from OpenJPEG or their software vendors as soon as they are released. In the absence of patches, organizations should implement strict input validation and filtering to block or quarantine untrusted JPEG 2000 images from external or unverified sources before processing. Employing sandboxing techniques to isolate image decoding processes can limit the impact of resource exhaustion. Monitoring resource usage patterns during image processing can help detect anomalous spikes indicative of exploitation attempts. Additionally, organizations should review and harden user interaction workflows that involve opening or processing image files, including user training to avoid opening suspicious images. Network-level controls, such as restricting image uploads or downloads from untrusted sources, can further reduce exposure. Finally, integrating rate limiting and timeout mechanisms in image processing services can prevent prolonged resource consumption caused by malicious inputs.