![]() The best way to reduce the risk of exploitation is to ensure all your software is up to date, so any discovered vulnerabilities are promptly fixed before they can be widely exploited. Any file format can be exploited, even ones you don't expect. ![]() In fact, they usually skip files that are not executable. They do not necessarily contain any tell-tale signs such as visible embedded scripts or suspicious strings, and antivirus will rarely be able to detect them. Unfortunately, it is not possible to manually detect a malicious file of this sort. The CVE details page gives some general information about its impact:ĭjVuLibre before 3.5.25.3, as used in Evince, Sumatra PDF Reader, VuDroid, and other products, allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted DjVu (aka. It only works locally without going through the server. This DjVu Viewer does not save or share the file you select. The interface has a plain and regular structure. It is quite easy to use and comprehend this app. ![]() The vulnerability, as reported by Microsoft, was a memory corruption bug that allowed for code execution. The DjVu Viewer is an app which is designed specifically to open and view the contents of DjVu files. A historical example is CVE-2012-6535, which affected the popular DjVuLibre library, used by many document viewers. Many viewers use the same library, making a vulnerability in a single library relevant to large number of viewers. While, as others have mentioned, it is designed not to have any executable code, a vulnerability in a DjVu parser can be used to exploit the viewer. DjVu is an open source file format that is currently maintained by Caminova and was originally developed by Lizard and AT&T to save scanned documents that. Syntax of the signature definition language you can read here.Yes, a DjVu file can be dangerous. This example just specifies DJVU start signature and calculates file size based on the first data chunk. Signature, must be 41 54 26 54 hex ("AT&T")ĬhunkId, must be 46 4F 52 4D hex ("FORM")Ĭhunk size (length of the data), big-endianĭjVu v3 Specifications File Recovery Custom Scripting Example Thus total DJVU file size is 12+94,368=94,380 bytes, and reading of all 94,380 consecutive bytes startingįrom the position of detected AT&T header provide us with all DjVu file data, provided that file is not fragmented. Data offset is 12 (dec) from the file beginning. The chunk size is big-endian value (highest byte first), which gives size of data 94,368 dec. ![]() Next to it, at offset 4, there is a tag FORM (hex: 46, 4F, 52, 4D) which points to the data chunk.ĭata chunk consists of a chunk size at absolute offset 8 (hex: 00, 01, 70, A0) followed by actual data. When inspecting example.djvu file's text data using any Hex Viewer, like Disk Editor, which is included in File Recovery package, we can see it starts with a tag AT&T (hex: 41, 54, 26, 54). By adding data size for the first chunk to a data offset (12 for the first chunk) we get the total DjVu file size. Data chunk has its data size at offset 4 (from chunk start) or, for the first chunk at offset 8 (from the file beginning).Ĭhunk size is big-endian (highest byte first). DjVu has been promoted as an alternative to PDF, promising smaller files than PDF for most scanned documents.ĭjVu Document files must have a signature (tag) AT&T at the beginning of the document followed by FORM tag which points to the data chunk. Browse DjVu files without any additional tools or plugins Based on the DjVu viewer implementation for Java by. ![]() Readable images to be stored in a minimum of space, so that they can be made available on the web. It uses technologies such as image layer separation of text and background/images, progressive loading,Īrithmetic coding, and lossy compression for bitonal (monochrome) images. DjVu eBook Signature Format: Specification & DjVu Recovery ExampleĭjVu is a computer file format designed primarily to store scanned documents and books,Įspecially those containing a combination of text, line drawings, indexed color images, and photographs. ![]()
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