CVE-2015-5700 in mktexlsr
Summary
by MITRE
mktexlsr revision 36855, and before revision 36626 as packaged in texlive allows local users to write to arbitrary files via a symlink attack.
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Analysis
by VulDB Data Team • 12/16/2022
The vulnerability identified as CVE-2015-5700 affects the mktexlsr utility within the TeX Live distribution, specifically in revision 36855 and earlier versions. This flaw represents a classic symlink attack vulnerability that enables local attackers to manipulate file operations by creating symbolic links in strategic locations. The mktexlsr utility is responsible for maintaining the TeX directory structure and generating the necessary database files for the TeX system to function properly. When this utility processes directory listings, it fails to properly validate file paths, allowing malicious users to exploit the system through symlink manipulation.
The technical implementation of this vulnerability stems from inadequate path validation within the mktexlsr utility's file handling mechanisms. When the utility encounters directory entries during its processing, it does not sufficiently verify whether the targets of symbolic links point to legitimate files or if they are maliciously crafted symlinks. This weakness creates an opportunity for privilege escalation attacks where local users can manipulate the utility's behavior to write content to arbitrary files on the system. The vulnerability operates under the principle of time-of-check to time-of-use race conditions, where the utility checks for file existence before performing operations that could be exploited through symlink manipulation.
From an operational perspective, this vulnerability poses significant security risks to systems running affected versions of TeX Live. Local attackers with minimal privileges can potentially write to critical system files, configuration files, or even system binaries, depending on the permissions and context in which the mktexlsr utility operates. The impact extends beyond simple file manipulation as it can enable attackers to establish persistent access or cause system instability through targeted file corruption. The vulnerability is particularly concerning in multi-user environments where TeX Live is commonly installed and used by various system users, as it provides a vector for privilege escalation and unauthorized system modifications.
The security implications of CVE-2015-5700 align with CWE-59 and CWE-367 categories, which encompass path traversal and time-of-check to time-of-use race conditions respectively. This vulnerability also maps to ATT&CK technique T1068, which involves exploiting local system privileges to gain elevated access. The attack vector demonstrates the importance of proper file system access controls and the need for utilities to validate file paths thoroughly. Organizations should implement immediate mitigations including updating to patched versions of TeX Live, restricting write permissions on TeX system directories, and monitoring for unauthorized file modifications. Additionally, system administrators should conduct regular security audits to identify similar vulnerabilities in other system utilities that perform file operations without proper path validation, as this represents a common pattern in privilege escalation attacks.