CVE-2025-53367 is an out-of-bounds (OOB) write vulnerability classified under CWE-787 and CWE-125 affecting DjvuNet's DjVuLibre, a GPL-licensed implementation of the DjVu document and image format. The vulnerability resides in the MMRDecoder::scanruns method, where the 'xr' pointer is not properly validated against the bounds of the allocated buffer. This improper bounds checking allows writes beyond the allocated heap memory, causing heap corruption. Additionally, an out-of-bounds read via the 'pr' pointer is possible due to the same lack of boundary validation. Such memory corruption can lead to unpredictable behavior including crashes, data corruption, or potentially arbitrary code execution if exploited. The vulnerability affects all versions prior to 3.5.29, which includes a patch that corrects the pointer boundary checks. The CVSS 4.0 score is 8.4 (high severity), reflecting the significant impact on confidentiality, integrity, and availability, combined with the requirement for local access and user interaction but no privileges or authentication. Although no exploits are currently known in the wild, the nature of heap corruption vulnerabilities makes this a serious concern for environments processing untrusted DjVu files. Attackers could craft malicious DjVu documents to trigger this flaw, potentially compromising systems that rely on DjVuLibre for document rendering or processing.

For European organizations, this vulnerability poses a substantial risk, especially those in sectors such as publishing, digital archiving, government, and any industry relying on DjVu format for document distribution or archival. Heap corruption can lead to denial of service, data integrity issues, or remote code execution if combined with other vulnerabilities or exploitation techniques. Since DjVuLibre is open source and widely used in various Linux distributions and document management systems, organizations using outdated versions are vulnerable. The requirement for local access and user interaction limits remote exploitation but does not eliminate risk, as phishing or social engineering could induce users to open malicious DjVu files. The impact on confidentiality and integrity is high, potentially exposing sensitive document contents or enabling attackers to manipulate document processing workflows. Availability may also be affected due to crashes or system instability. European entities with critical infrastructure or sensitive data processed via DjVuLibre should consider this vulnerability a priority for patching to prevent targeted attacks or accidental compromise.

The primary mitigation is to upgrade DjVuLibre to version 3.5.29 or later, where the vulnerability has been patched. Organizations should audit their environments to identify all instances of DjVuLibre and ensure they are updated promptly. For environments where immediate upgrade is not feasible, implementing strict file handling policies to block or quarantine untrusted DjVu files can reduce risk. Employ endpoint protection solutions that monitor for abnormal application behavior or memory corruption attempts. User training to avoid opening suspicious DjVu documents is critical due to the user interaction requirement. Additionally, sandboxing document viewers or running them with least privilege can limit the impact of exploitation. Monitoring logs for crashes or unusual behavior in document processing applications can help detect exploitation attempts. Finally, integrating vulnerability management processes to track and remediate such issues proactively is recommended.