CVE-2007-2833 in Linux
Summary
by MITRE
Emacs 21 allows user-assisted attackers to cause a denial of service (crash) via certain crafted images, as demonstrated via a GIF image in vm mode, related to image size calculation.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability identified as CVE-2007-2833 affects GNU Emacs version 21 and represents a classic buffer overflow condition that can be triggered through crafted image files. This flaw exists within the image handling subsystem of the text editor, specifically when processing GIF images in vm mode, which is a mail reading mode within Emacs. The vulnerability stems from inadequate input validation and improper memory management during image size calculations, creating a scenario where maliciously constructed image data can cause the application to crash or become unresponsive. The issue is classified as user-assisted since it requires an attacker to convince a victim to open a specially crafted image file, typically through email attachments or shared documents. This type of vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions where insufficient boundary checking allows attackers to overwrite adjacent memory locations. The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially be leveraged to execute arbitrary code if the buffer overflow occurs in a manner that allows code injection.
The technical implementation of this vulnerability occurs when Emacs attempts to parse and display a GIF image file that has been deliberately constructed with malformed dimensions or image data. During the image size calculation process, the application fails to properly validate the image headers and metadata, leading to integer overflow or underflow conditions that result in improper memory allocation. When the vm mode processes these crafted images, the application's memory management routines become corrupted, causing the program to terminate unexpectedly or enter an unstable state. The vulnerability demonstrates characteristics of the ATT&CK technique T1203, which involves the exploitation of software vulnerabilities to cause denial of service or system instability. The flaw is particularly concerning in email environments where users may inadvertently open malicious attachments, making this a significant risk for organizations that rely heavily on email communication and document sharing.
Mitigation strategies for this vulnerability must address both immediate defensive measures and long-term architectural improvements. System administrators should immediately upgrade to a patched version of GNU Emacs that contains proper input validation and memory boundary checking for image processing routines. The recommended approach includes implementing strict file format validation, limiting the maximum image dimensions that can be processed, and establishing proper memory allocation limits during image parsing. Organizations should also consider implementing email filtering mechanisms that can detect and quarantine suspicious image files, particularly those with unusual metadata or malformed headers. Additionally, regular security audits of software dependencies and third-party libraries should be conducted to identify similar vulnerabilities in other applications. The remediation process should include comprehensive testing of image handling capabilities with various file formats to ensure that similar buffer overflow conditions are not present in other parts of the application. This vulnerability highlights the importance of input validation and proper memory management in preventing both denial of service attacks and potential privilege escalation scenarios that could arise from more sophisticated exploitation techniques.