CVE-2008-1694 in Emacs
Summary
by MITRE
vcdiff in Emacs 20.7 to 22.1.50, when used with SCCS, allows local users to overwrite arbitrary files via a symlink attack on temporary files.
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability identified as CVE-2008-1694 represents a significant security flaw in the vcdiff utility bundled with Emacs versions ranging from 20.7 through 22.1.50. This issue specifically manifests when Emacs integrates with SCCS (Source Code Control System) for version control operations. The core problem stems from insufficient validation of temporary file creation processes, creating opportunities for malicious local users to exploit symbolic link attacks against the system's file permissions and access controls. The vulnerability is classified under CWE-59 as a "Improper Link Resolution Before File Access" which directly impacts the integrity of file operations within the Emacs environment.
The technical implementation of this vulnerability occurs when the vcdiff utility creates temporary files during SCCS operations without properly verifying the existence or ownership of these temporary files before writing to them. When a local attacker can manipulate the symbolic link structure within the temporary file directory, they can redirect file write operations to arbitrary locations on the filesystem. This allows attackers to overwrite files with malicious content, potentially compromising system integrity, confidentiality, and availability. The flaw operates at the intersection of file system permissions, temporary file handling, and privilege escalation mechanisms.
The operational impact of CVE-2008-1694 extends beyond simple file overwriting capabilities, as it provides attackers with a persistent means of modifying system files, configuration data, or user documents. The vulnerability is particularly dangerous in multi-user environments where Emacs is commonly used for collaborative development work, as it can enable attackers to compromise other users' work or inject malicious code into version-controlled repositories. This type of attack aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1546.004 for "Event Triggered Execution: File System Permissions Changes" in the context of privilege escalation and persistence mechanisms.
Mitigation strategies for this vulnerability must address both immediate operational concerns and long-term security posture improvements. System administrators should immediately update to patched versions of Emacs, specifically versions beyond 22.1.50 where the vulnerability has been resolved. Additionally, implementing proper temporary file handling mechanisms such as creating temporary files with unique names, using secure file creation primitives, and ensuring proper file ownership and permissions can prevent exploitation. The remediation approach should follow security best practices outlined in NIST SP 800-53 and ISO/IEC 27001 standards for secure file handling and temporary file management. Organizations should also consider implementing monitoring solutions to detect suspicious file creation patterns and symbolic link manipulation activities that may indicate exploitation attempts.