CVE-2025-53367 is a high-severity vulnerability affecting DjVuLibre, a GPL-licensed implementation of the DjVu format used for distributing documents and images on the web. The vulnerability resides in the MMRDecoder::scanruns method prior to version 3.5.29. Specifically, the method fails to properly validate that the 'xr' pointer remains within the bounds of the allocated buffer during decoding operations. This lack of bounds checking leads to an out-of-bounds (OOB) write condition, where memory beyond the intended buffer is overwritten, causing heap corruption. Additionally, an out-of-bounds read is also possible due to the same pointer mismanagement. Heap corruption vulnerabilities are particularly dangerous as they can be exploited to manipulate program execution flow, potentially allowing attackers to execute arbitrary code or cause denial of service. The vulnerability does not require privileges or authentication but does require user interaction, as it is triggered by processing a maliciously crafted DjVu document. The issue has been patched in DjVuLibre version 3.5.29, and users of earlier versions are at risk. The CVSS 4.0 score is 8.4, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity but requiring user interaction. No known exploits are currently reported in the wild, but the nature of the vulnerability suggests potential for exploitation once weaponized. Given that DjVuLibre is used in various document viewers and processing tools, this vulnerability could be leveraged in targeted attacks involving malicious document distribution.

For European organizations, the impact of this vulnerability could be significant, especially for entities relying on DjVuLibre for document viewing, archival, or processing workflows. Exploitation could lead to arbitrary code execution, allowing attackers to compromise affected systems, steal sensitive information, or disrupt operations. Sectors such as government, legal, publishing, and education—where DjVu format documents might be prevalent—are particularly at risk. The heap corruption could also cause application crashes, leading to denial of service conditions that disrupt business continuity. Since the vulnerability requires user interaction, phishing or social engineering campaigns distributing malicious DjVu files could be a likely attack vector. The confidentiality, integrity, and availability of critical documents and systems could be compromised, potentially leading to data breaches or operational outages. Moreover, the vulnerability’s presence in open-source software used across multiple platforms increases the attack surface for European organizations.

European organizations should immediately verify if any systems use DjVuLibre versions prior to 3.5.29. Specific mitigation steps include: 1) Upgrade all DjVuLibre deployments to version 3.5.29 or later to apply the official patch. 2) Implement strict file handling policies that restrict or scan DjVu files before opening, using antivirus and sandboxing solutions capable of detecting malformed DjVu documents. 3) Educate users about the risks of opening unsolicited or unexpected DjVu files, emphasizing caution with email attachments and downloads. 4) Employ network-level protections such as email gateway filters to block or quarantine suspicious DjVu attachments. 5) Monitor logs and endpoint behavior for signs of exploitation attempts, including crashes or anomalous process activity related to document viewers. 6) For organizations with custom or legacy software integrating DjVuLibre, conduct code audits and testing to ensure safe handling of DjVu files. These targeted mitigations go beyond generic advice by focusing on patch management, user awareness, and layered defenses specific to the DjVu format and this vulnerability.