CVE-2011-1011 in policycoreutils
Summary
by MITRE
The seunshare_mount function in sandbox/seunshare.c in seunshare in certain Red Hat packages of policycoreutils 2.0.83 and earlier in Red Hat Enterprise Linux (RHEL) 6 and earlier, and Fedora 14 and earlier, mounts a new directory on top of /tmp without assigning root ownership and the sticky bit to this new directory, which allows local users to replace or delete arbitrary /tmp files, and consequently cause a denial of service or possibly gain privileges, by running a setuid application that relies on /tmp, as demonstrated by the ksu application.
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Analysis
by VulDB Data Team • 01/16/2025
The vulnerability described in CVE-2011-1011 resides within the seunshare component of policycoreutils, specifically in the seunshare_mount function located in sandbox/seunshare.c. This flaw affects Red Hat Enterprise Linux versions 6 and earlier, as well as Fedora 14 and earlier releases. The issue stems from improper directory permissions during the mounting process where a new directory is created atop the /tmp filesystem without establishing proper root ownership or setting the sticky bit. This configuration creates a significant security weakness that can be exploited by local attackers to manipulate critical system resources. The vulnerability is classified under CWE-276, which addresses improper file permissions, and represents a classic case of insufficient privilege separation in system utilities.
The technical implementation of this vulnerability involves the seunshare_mount function failing to properly secure the temporary directory it creates. When mounting a new filesystem on top of /tmp, the function does not assign root ownership to the newly created directory nor does it set the sticky bit that typically prevents users from deleting or replacing files they do not own within a shared directory. This omission allows any local user to create files in the mounted directory that can subsequently be used to replace or delete files in the underlying /tmp directory. The attack vector becomes particularly dangerous when combined with setuid applications that depend on /tmp for their operation, as demonstrated with the ksu application. This represents a privilege escalation pathway that aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation of system utilities.
The operational impact of this vulnerability extends beyond simple denial of service to potential privilege escalation scenarios. Local attackers can exploit this weakness to replace critical system files or manipulate temporary files used by setuid applications, potentially allowing them to execute arbitrary code with elevated privileges. The consequences can range from service disruption through file deletion to full system compromise when combined with other exploitation techniques. The vulnerability affects systems running older versions of policycoreutils where the seunshare utility is present and actively used, particularly in environments where setuid applications like ksu are deployed. This flaw demonstrates the critical importance of proper file system permissions and the potential for seemingly minor configuration oversights to create significant security risks.
Mitigation strategies for CVE-2011-1011 involve immediate patching of affected policycoreutils packages to versions that properly implement directory ownership and permission settings. System administrators should ensure that all Red Hat Enterprise Linux 6 and earlier, as well as Fedora 14 and earlier systems, are updated to patched versions of policycoreutils. Additionally, monitoring for unauthorized use of the seunshare utility and implementing proper file system auditing can help detect exploitation attempts. The remediation approach should follow standard vulnerability management procedures including vulnerability scanning, risk assessment, and coordinated patch deployment. Organizations should also consider implementing additional security controls such as mandatory access controls and file integrity monitoring to detect and prevent exploitation of similar permission-based vulnerabilities. This vulnerability serves as a reminder of the importance of proper privilege separation and secure coding practices in system utilities that handle temporary file operations.