CVE-2018-18520 in elfutils
Summary
by MITRE
An Invalid Memory Address Dereference exists in the function elf_end in libelf in elfutils through v0.174. Although eu-size is intended to support ar files inside ar files, handle_ar in size.c closes the outer ar file before handling all inner entries. The vulnerability allows attackers to cause a denial of service (application crash) with a crafted ELF file.
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Analysis
by VulDB Data Team • 05/30/2023
The vulnerability identified as CVE-2018-18520 represents a critical memory management flaw within the elfutils library version 0.174 and earlier. This issue manifests specifically within the elf_end function of the libelf component, where an invalid memory address dereference occurs under certain conditions. The flaw is particularly concerning because it can be exploited to trigger a denial of service condition that results in application crashes, effectively disrupting system operations and potentially providing attackers with a means to destabilize systems that rely on proper ELF file processing.
The technical root cause of this vulnerability stems from improper resource management within the eu-size utility's handling of archive files. The handle_ar function in size.c demonstrates a problematic pattern where the outer ar file is closed prematurely before all inner entries have been properly processed. This creates a scenario where subsequent operations attempt to access memory locations that have already been deallocated, leading to the invalid memory address dereference. The vulnerability specifically impacts the processing of ar files that contain nested ar files, where the outer archive contains inner archives that must be examined. This flaw directly maps to CWE-476, which addresses NULL pointer dereference conditions, though in this case it involves invalid memory addresses rather than null pointers.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be leveraged to create persistent denial of service conditions within systems that process ELF files. Attackers can craft malicious ELF files that, when processed by vulnerable versions of eu-size or other tools within the elfutils suite, will trigger the memory corruption and subsequent crash. This vulnerability particularly affects systems where automated processing of binary files occurs, such as security scanning systems, build environments, or any infrastructure that handles untrusted ELF content. The attack vector requires minimal privileges and can be executed through normal file processing workflows, making it particularly dangerous in automated environments.
Mitigation strategies for CVE-2018-18520 should prioritize immediate patching of affected systems, with the most effective solution being the upgrade to elfutils version 0.175 or later where this vulnerability has been resolved. Organizations should also implement defensive measures such as input validation and sandboxed processing of untrusted ELF files to prevent exploitation. The fix typically involves ensuring proper resource management in the handle_ar function to prevent premature closure of archive files before all nested entries have been processed. Security teams should also monitor for potential exploitation attempts through file processing workflows and consider implementing additional logging and alerting mechanisms around ELF file handling operations. This vulnerability demonstrates the importance of proper resource management in binary processing utilities and aligns with ATT&CK technique T1059.007 for execution through command and scripting interpreter, particularly in environments where automated processing of binary files occurs.