CVE-2014-4150 in Scheme 48
Summary
by MITRE
The scheme48-send-definition function in cmuscheme48.el in Scheme 48 allows local users to write to arbitrary files via a symlink attack on /tmp/s48lose.tmp.
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Analysis
by VulDB Data Team • 03/08/2020
The vulnerability identified as CVE-2014-4150 resides within the cmuscheme48.el component of Scheme 48, a functional programming environment that integrates with emacs. This flaw manifests as a local privilege escalation vector that exploits insecure temporary file handling mechanisms. The vulnerability specifically affects the scheme48-send-definition function which creates temporary files in the /tmp directory without proper security checks, making it susceptible to symlink attacks that can redirect file operations to arbitrary locations on the filesystem.
The technical implementation of this vulnerability involves the creation of a temporary file named /tmp/s48lose.tmp by the scheme48-send-definition function during its operation. When a local attacker can manipulate the symbolic link structure of this temporary file, they can redirect the file writing operations to any location they choose on the system. This occurs because the function does not validate whether the temporary file exists as a symlink or if it points to a location outside of the intended scope, allowing attackers to place malicious content at arbitrary filesystem locations. The flaw represents a classic race condition vulnerability where the timing between file creation and access creates an exploitable window for symlink manipulation.
The operational impact of this vulnerability extends beyond simple file system manipulation as it provides local attackers with the ability to write arbitrary content to any location where the compromised application has write permissions. This can lead to privilege escalation scenarios where attackers can modify system files, inject malicious code into legitimate applications, or establish persistent backdoors within the system. The vulnerability is particularly concerning in environments where Scheme 48 is used with elevated privileges or where multiple users share the same system resources, as it can be exploited to gain unauthorized access to sensitive system components.
Mitigation strategies for this vulnerability should focus on implementing proper temporary file handling practices that prevent symlink attacks. The recommended approach involves creating temporary files with secure permissions and using atomic operations that prevent symbolic link manipulation during file creation. Security practitioners should ensure that applications create temporary files using secure methods such as mkstemp or similar functions that guarantee file ownership and prevent race conditions. Additionally, system administrators should review and restrict write permissions for the /tmp directory to minimize the potential impact of such vulnerabilities. This vulnerability aligns with CWE-377: Insecure Temporary Files and CWE-378: Poor File Permissions for Temporary Files, both of which are categorized under the broader category of insecure file handling practices. The attack vector can be mapped to ATT&CK technique T1059.006 for execution through scripting languages and T1078 for legitimate credentials use, depending on the specific exploitation scenario. Organizations should implement regular security audits of their Scheme 48 installations and ensure that all system components are updated to versions that address this specific vulnerability.