CVE-2008-5135 in os-prober
Summary
by MITRE
** DISPUTED ** os-prober in os-prober 1.17 allows local users to overwrite arbitrary files via a symlink attack on the (1) /tmp/mounted-map or (2) /tmp/raided-map temporary file. NOTE: the vendor disputes this issue, stating "the insecure code path should only ever run inside a d-i environment, which has no non-root users."
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Analysis
by VulDB Data Team • 08/07/2024
The vulnerability identified as CVE-2008-5135 pertains to a file overwrite issue within the os-prober utility version 1.17, specifically targeting temporary files used during system boot process analysis. This flaw represents a classic symlink attack vector that could potentially allow local users to manipulate critical system components through carefully crafted symbolic link constructions. The vulnerability occurs in the context of operating system detection and boot management processes where the system attempts to identify and catalog available operating systems on the local machine.
The technical implementation of this vulnerability stems from improper handling of temporary files in the os-prober utility. When the system processes multiple operating systems during boot detection, it creates temporary files at predictable locations such as /tmp/mounted-map and /tmp/raided-map. These temporary files are susceptible to race conditions where malicious local users can create symbolic links pointing to arbitrary files before the legitimate file operations occur. This type of vulnerability aligns with CWE-377, which addresses insecure temporary file handling practices, and specifically relates to CWE-378 which covers the creation of temporary files with insecure permissions. The flaw demonstrates poor input validation and inadequate file access controls during temporary file creation and manipulation phases.
The operational impact of this vulnerability extends beyond simple file overwrites, as it could potentially enable privilege escalation or system compromise depending on the target files being overwritten. When attackers successfully exploit this vulnerability, they can modify critical system configuration files, boot loaders, or other sensitive components that influence system behavior during startup. The attack vector specifically targets local users with limited privileges, making it particularly concerning in multi-user environments where privilege separation is expected. This vulnerability represents a significant concern for system administrators who must ensure that temporary file handling does not create opportunities for unauthorized system modification. The potential for exploitation increases when system administrators or automated processes run os-prober with elevated privileges during boot processes.
The vendor response dismissing this issue as only occurring within d-i environments demonstrates a misunderstanding of the broader threat landscape. While the specific exploitation might be limited to Debian installer contexts, the fundamental flaw in temporary file handling remains exploitable in other scenarios where non-root users have access to systems running os-prober. The ATT&CK framework would categorize this as a privilege escalation technique through file system manipulation, specifically under the T1068 category for privilege escalation. Security practitioners should consider implementing additional controls such as proper file permissions, secure temporary file creation practices, and monitoring for suspicious file access patterns. Mitigation strategies should include ensuring that temporary files are created with proper permissions, using secure temporary file creation functions, and implementing proper access controls to prevent symlink attacks. The vulnerability highlights the importance of secure coding practices in system utilities and the need for thorough security reviews of boot-time processes where privilege escalation opportunities exist.