CVE-2015-1572 in Ubuntu Linux
Summary
by MITRE
Heap-based buffer overflow in closefs.c in the libext2fs library in e2fsprogs before 1.42.12 allows local users to execute arbitrary code by causing a crafted block group descriptor to be marked as dirty. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-0247.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2015-1572 represents a critical heap-based buffer overflow within the libext2fs library component of e2fsprogs software suite. This flaw resides in the closefs.c file and affects versions prior to 1.42.12, creating a significant security risk for systems utilizing ext2 filesystems. The vulnerability specifically manifests when a crafted block group descriptor is marked as dirty, triggering memory corruption that can be exploited by local attackers to execute arbitrary code with elevated privileges. The issue stems from an incomplete remediation of a previous vulnerability CVE-2015-0247, indicating that the initial fix failed to address all potential code paths that could lead to buffer overflow conditions.
The technical implementation of this vulnerability involves improper bounds checking within the filesystem library's handling of block group descriptors during filesystem closure operations. When a maliciously crafted block group descriptor is processed and marked as dirty, the libext2fs library fails to validate the descriptor's size or boundaries before performing memory operations. This oversight allows attackers to write beyond allocated heap memory regions, potentially corrupting adjacent memory structures and enabling code execution. The heap overflow occurs because the library assumes descriptor sizes will remain within expected parameters, failing to account for malformed or crafted inputs that could exceed allocated buffer limits. This type of vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a classic example of inadequate input validation in memory management operations.
The operational impact of CVE-2015-1572 extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. Local attackers with minimal privileges can exploit this vulnerability to gain root access on affected systems, as the overflow occurs within a library that is part of the core filesystem utilities. This makes the vulnerability particularly dangerous in multi-user environments where attackers might attempt to leverage the flaw to establish persistent access or escalate their privileges to administrative levels. The vulnerability also impacts system stability, as memory corruption can lead to crashes or unpredictable behavior in filesystem operations. From an attack perspective, this vulnerability fits within the ATT&CK framework under privilege escalation techniques, specifically targeting the execution of malicious code through memory corruption vulnerabilities.
Mitigation strategies for CVE-2015-1572 focus primarily on immediate software updates and system hardening measures. The most effective remediation involves upgrading to e2fsprogs version 1.42.12 or later, which contains the complete fix addressing both the original CVE-2015-0247 and this subsequent vulnerability. System administrators should also implement monitoring for suspicious filesystem operations and consider implementing additional security controls such as file system access controls and privilege separation mechanisms. The vulnerability demonstrates the importance of thorough vulnerability analysis and testing, as incomplete fixes can leave systems exposed to continued exploitation. Organizations should also consider implementing memory protection mechanisms like stack canaries and address space layout randomization to reduce exploitability even if other mitigations are not immediately available. Regular security assessments and vulnerability scanning should be conducted to identify similar incomplete fixes in other system components and prevent future exploitation opportunities.