CVE-2024-56378 identifies a vulnerability in the Poppler PDF rendering library, specifically in the libpoppler.so shared object up to version 24.12.0. The issue is an out-of-bounds read (CWE-125) occurring in the JBIG2Bitmap::combine function within the JBIG2Stream.cc source file. JBIG2 is a compression format used for bi-level images in PDFs, and Poppler’s JBIG2Stream component handles decoding these images. The vulnerability arises when malformed or maliciously crafted JBIG2 streams cause the combine function to read memory beyond the allocated buffer boundaries. This can lead to integrity violations, such as incorrect processing or corruption of PDF content, though it does not directly expose confidential data or cause denial of service. The CVSS 3.1 base score is 4.3 (medium), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), no confidentiality impact (C:N), integrity impact (I:L), and no availability impact (A:N). No known exploits have been reported in the wild, and no patches were available at the time of disclosure. The vulnerability affects any system using vulnerable Poppler versions for PDF rendering or processing, including Linux distributions, embedded systems, and applications relying on Poppler as a backend. Given Poppler’s widespread use in open-source environments and PDF processing tools, this vulnerability could be leveraged in targeted attacks involving malicious PDF documents.

For European organizations, the primary impact is on the integrity of PDF processing workflows. Sectors such as government, finance, legal, and publishing that heavily rely on PDF documents and open-source tools may face risks of document corruption or manipulation if malicious PDFs exploit this vulnerability. Although confidentiality and availability are not directly affected, integrity breaches could undermine trust in document authenticity and processing pipelines. Organizations using Poppler in automated document processing, archival systems, or web services that render PDFs are particularly at risk. The vulnerability’s network vector and lack of user interaction requirement increase the risk of remote exploitation, especially in environments where PDF files are ingested from untrusted sources. However, the requirement for low privileges limits exploitation to contexts where an attacker has some level of access, reducing the overall threat scope. The absence of known exploits and patches currently lowers immediate risk but underscores the need for vigilance and timely remediation once fixes are released.

1. Monitor official Poppler repositories and security advisories for patches addressing CVE-2024-56378 and apply updates promptly once available. 2. Until patches are released, restrict exposure by limiting network access to services that process PDFs using vulnerable Poppler versions. 3. Implement sandboxing or containerization for PDF processing applications to contain potential exploitation effects. 4. Employ input validation and filtering to block or quarantine suspicious or malformed PDF files, especially those containing JBIG2 streams. 5. Use alternative PDF rendering libraries or tools that are not affected, if feasible, as a temporary mitigation. 6. Conduct internal audits to identify all systems and applications using Poppler and assess their exposure. 7. Educate users and administrators about the risks of processing untrusted PDFs and encourage cautious handling of email attachments and downloads. 8. Integrate runtime monitoring to detect anomalous behavior indicative of exploitation attempts targeting PDF processing components.