CVE-2001-1551 in Linux
Summary
by MITRE
Linux kernel 2.2.19 enables CAP_SYS_RESOURCE for setuid processes, which allows local users to exceed disk quota restrictions during execution of setuid programs.
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Analysis
by VulDB Data Team • 06/05/2018
The vulnerability described in CVE-2001-1551 represents a critical privilege escalation flaw within the Linux kernel version 2.2.19 that fundamentally undermines the security model of setuid programs. This issue arises from an improper implementation of capability handling within the kernel's security framework, specifically concerning the CAP_SYS_RESOURCE capability which grants extensive system-level privileges including the ability to override resource limits and disk quotas. The flaw exists in the kernel's process management subsystem where setuid programs are executed with elevated privileges that should be restricted to prevent unauthorized access to system resources.
The technical implementation of this vulnerability stems from the kernel's failure to properly drop capabilities when transitioning from privileged to unprivileged execution contexts for setuid processes. When a setuid program executes, the kernel should strip away unnecessary privileges to prevent escalation attacks, but in version 2.2.19, the CAP_SYS_RESOURCE capability is inadvertently retained during this transition. This capability allows processes to bypass disk quota restrictions and manipulate system resources in ways that should be restricted to root or administrative users only. The vulnerability is particularly dangerous because it operates at the kernel level, meaning that local users with minimal privileges can exploit this flaw to gain unauthorized access to system resources without requiring direct root access or complex attack vectors.
From an operational impact perspective, this vulnerability creates significant security risks for systems running the affected kernel version, as it allows local attackers to consume excessive disk space and system resources beyond their allocated quotas. The exploitation of this vulnerability can lead to denial of service conditions where legitimate users are unable to access system resources due to quota exhaustion, while simultaneously allowing attackers to consume system resources without detection. The flaw also opens possibilities for privilege escalation attacks where users can potentially gain root access through carefully crafted setuid programs that leverage the retained capabilities. This vulnerability directly violates the principle of least privilege and undermines the fundamental security assumptions of Unix-like operating systems.
Mitigation strategies for this vulnerability require immediate kernel upgrades to patched versions that properly handle capability transitions for setuid processes, as well as comprehensive system hardening measures. System administrators should implement strict monitoring of disk usage and quota violations to detect potential exploitation attempts, while also reviewing and restricting setuid program installations on affected systems. The vulnerability aligns with CWE-257, which addresses insecure storage of passwords and credentials, and maps to ATT&CK technique T1068, which covers privilege escalation through local exploits. Organizations should also implement automated patch management systems to ensure timely deployment of kernel updates and establish security monitoring protocols that can detect anomalous resource consumption patterns indicative of quota bypass attempts. The remediation process involves not only updating kernel versions but also conducting thorough security audits of setuid programs to identify and remove unnecessary privileged executables that could be exploited in conjunction with this vulnerability.