CVE-2016-9558 in libdwarf
Summary
by MITRE
(1) libdwarf/dwarf_leb.c and (2) dwarfdump/print_frames.c in libdwarf before 20161124 allow remote attackers to have unspecified impact via a crafted bit pattern in a signed leb number, aka a "negation overflow."
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Analysis
by VulDB Data Team • 09/02/2020
The vulnerability identified as CVE-2016-9558 affects the libdwarf library, a critical component used for processing debug information in binary files, particularly within the dwarf debugging format. This library serves as a foundational element for numerous security tools, development environments, and system diagnostics utilities that rely on parsing and interpreting debug data. The flaw resides in two specific files within the library: libdwarf/dwarf_leb.c which handles leb128 encoding and decoding operations, and dwarfdump/print_frames.c which processes frame information within debug data. These components are essential for proper parsing of binary executables and shared libraries, making this vulnerability particularly concerning for systems that process untrusted binary data.
The technical root cause of this vulnerability stems from improper handling of signed leb128 numbers, a variable-length encoding scheme commonly used in dwarf debug information to represent integers efficiently. When processing crafted bit patterns in signed leb128 encoded values, the library fails to properly validate or handle negative overflow conditions during the decoding process. This negation overflow occurs when the library attempts to convert a malformed leb128 value into a signed integer, resulting in unexpected behavior that can manifest as memory corruption, arbitrary code execution, or denial of service conditions. The vulnerability specifically targets the interpretation of signed leb128 values where the most significant bit indicates a negative number, but the processing logic does not adequately account for potential overflow conditions during the conversion process. This flaw aligns with CWE-191, which describes integer underflow conditions, and represents a classic example of improper integer handling in cryptographic and binary parsing contexts.
The operational impact of this vulnerability extends across multiple domains where libdwarf is utilized, including security analysis tools, binary exploitation frameworks, software development environments, and system diagnostic utilities. Attackers can exploit this weakness by crafting malicious binary files containing specially crafted leb128 values that trigger the overflow condition when processed by vulnerable applications. The consequences range from denial of service attacks that crash applications parsing debug information to more severe scenarios where memory corruption could lead to arbitrary code execution, particularly in applications that directly process untrusted binary data. This vulnerability particularly affects tools such as dwarfdump, which is commonly used for examining debug information in binary files, and security frameworks that rely on libdwarf for binary analysis. The impact is amplified because many development and security tools use libdwarf as a core dependency, creating a wide attack surface that extends beyond just the direct users of the library.
Mitigation strategies for this vulnerability primarily involve updating to libdwarf version 20161124 or later, which contains the necessary patches to properly handle signed leb128 overflow conditions. System administrators and security teams should prioritize updating all affected applications and tools that depend on libdwarf, particularly those handling untrusted binary data. Additional defensive measures include implementing input validation and sanitization for debug information processing, using sandboxing techniques when parsing binary files, and monitoring for unusual behavior in applications that utilize libdwarf. From an ATT&CK framework perspective, this vulnerability maps to techniques involving code injection and privilege escalation through binary manipulation, as attackers could potentially leverage the overflow to execute malicious code within applications that process debug information. Organizations should also consider implementing runtime protections and memory safety mechanisms such as address space layout randomization, stack canaries, and control flow integrity checks to reduce the potential impact of exploitation attempts. The vulnerability demonstrates the critical importance of proper integer handling in low-level binary processing libraries and serves as a reminder of the need for comprehensive testing and validation of encoding/decoding routines in security-critical software components.