CVE-2017-9778 in Debugger
Summary
by MITRE
GNU Debugger (GDB) 8.0 and earlier fails to detect a negative length field in a DWARF section. A malformed section in an ELF binary or a core file can cause GDB to repeatedly allocate memory until a process limit is reached. This can, for example, impede efforts to analyze malware with GDB.
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Analysis
by VulDB Data Team • 10/19/2019
The vulnerability identified as CVE-2017-9778 represents a critical memory allocation flaw within GNU Debugger version 8.0 and earlier implementations. This issue stems from GDB's inadequate validation of DWARF debugging information sections within ELF binaries and core files. The flaw specifically manifests when GDB encounters a negative length field in DWARF sections, which should normally trigger an immediate rejection of malformed data. However, the debugger fails to properly detect this condition, leading to a dangerous memory allocation behavior that can consume system resources rapidly.
The technical nature of this vulnerability places it firmly within CWE-129, which addresses insufficient validation of length fields, and CWE-772, concerning missing resource management. When GDB processes a malformed ELF binary or core file containing a negative DWARF length field, the debugger's parsing routine does not properly validate the length parameter before proceeding with memory allocation operations. This oversight allows the debugger to allocate memory repeatedly based on the invalid negative value, creating a memory exhaustion scenario that can eventually crash the debugger or render the system unresponsive.
The operational impact of this vulnerability extends far beyond simple debugging failures, particularly in malware analysis and forensic investigations. Security researchers and analysts who rely on GDB for examining suspicious binaries face significant risks when encountering malicious files that exploit this flaw. The memory exhaustion can prevent proper analysis of malware samples, effectively blocking security teams from understanding the behavior of potentially harmful code. This vulnerability directly impacts the ATT&CK technique T1059.006, which involves the use of debuggers and reverse engineering tools for malware analysis, as the debugger itself becomes compromised by the malicious input.
In practical exploitation scenarios, adversaries can craft ELF binaries or core files containing specifically crafted negative length fields in DWARF sections to trigger this memory exhaustion behavior. The vulnerability is particularly dangerous in automated analysis environments where multiple files are processed sequentially, as a single malicious file can cause cascading failures across entire analysis systems. The lack of proper bounds checking in GDB's DWARF section parsing creates an avenue for resource exhaustion attacks that can persistently degrade system performance or cause complete system crashes.
The recommended mitigations for this vulnerability include immediate upgrading to GDB version 8.1 or later, where the issue has been addressed through enhanced validation of DWARF section length fields. System administrators should implement additional safeguards such as sandboxing GDB executions and monitoring memory consumption during debugging sessions. Organizations conducting malware analysis should establish strict input validation procedures and consider using alternative debugging tools that have been verified to handle malformed input more robustly. The fix implemented in later GDB versions involves comprehensive validation of length fields within DWARF sections, ensuring that negative values are properly rejected before any memory allocation occurs, thereby preventing the resource exhaustion scenario that characterized the original vulnerability.