CVE-2017-12966 in ASN1C
Summary
by MITRE
The asn1f_lookup_symbol_impl function in asn1fix_retrieve.c in libasn1fix.a in asn1c 0.9.28 allows remote attackers to cause a denial of service (segmentation fault) via a crafted .asn1 file.
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Analysis
by VulDB Data Team • 11/09/2019
The vulnerability identified as CVE-2017-12966 resides within the asn1c 0.9.28 library, specifically in the asn1f_lookup_symbol_impl function located in asn1fix_retrieve.c. This flaw represents a classic buffer overflow condition that occurs during the processing of malformed asn1 files, creating a potential for remote denial of service attacks. The vulnerability manifests when the asn1c library attempts to parse crafted .asn1 files that contain malformed symbol references, leading to a segmentation fault that crashes the application. This issue falls under the category of improper input validation and memory management errors, which are commonly classified as CWE-121 and CWE-125 in the Common Weakness Enumeration framework. The attack vector is particularly concerning as it allows remote adversaries to trigger the vulnerability simply by providing a maliciously crafted asn1 file, making it accessible through network-based exploitation.
The technical implementation of this vulnerability stems from inadequate bounds checking within the asn1f_lookup_symbol_impl function. When processing symbol lookups in asn1 files, the function fails to properly validate the structure of symbol references in the input file, leading to memory corruption during the parsing process. The flaw occurs during the retrieval phase where the library attempts to resolve symbol references from the abstract syntax notation one files, which are commonly used in telecommunications and networking protocols for defining data structures. This particular function does not perform sufficient validation of array indices or pointer arithmetic, allowing an attacker to manipulate the parsing logic into accessing invalid memory locations. The vulnerability is particularly dangerous because it operates at the parsing layer of the asn1c library, which is widely used in various applications that process asn1 encoded data, including network protocols, security systems, and telecommunications infrastructure.
The operational impact of CVE-2017-12966 extends beyond simple service disruption, as it can be leveraged in broader attack scenarios within the MITRE ATT&CK framework under the T1499 category of Network Denial of Service. Systems that rely on asn1c for processing external data inputs become vulnerable to this attack, potentially affecting applications such as network management systems, security appliances, and telecommunications equipment that utilize asn1 encoding for protocol definitions. The vulnerability's remote exploitability means that attackers can trigger the segmentation fault from external networks without requiring local access to the target system. This characteristic makes it particularly attractive for attackers seeking to disrupt services or perform reconnaissance activities. Organizations using software that depends on the affected version of asn1c are at risk of experiencing service interruptions, application crashes, and potential data loss during the denial of service event. The impact is further amplified because the vulnerability affects the core parsing functionality of the library, meaning that any application utilizing this library for asn1 file processing could be compromised.
Mitigation strategies for CVE-2017-12966 should focus on immediate patching of the asn1c library to version 0.9.29 or later, which contains the necessary fixes for the buffer overflow vulnerability. System administrators should also implement network segmentation and access controls to limit exposure of systems that process external asn1 files, reducing the attack surface for potential exploitation. Input validation should be strengthened at the application level by implementing proper bounds checking and error handling for all asn1 file processing operations, ensuring that malformed files are rejected before they reach the vulnerable library functions. Organizations should also consider implementing monitoring and alerting mechanisms to detect unusual patterns of application crashes or segmentation faults that could indicate exploitation attempts. Additionally, the use of sandboxing techniques or containerization for applications that process external asn1 data can provide additional layers of protection by isolating the vulnerable components from the rest of the system infrastructure. Regular security assessments and vulnerability scanning should be conducted to identify any other potentially affected systems within the network environment that may be utilizing the vulnerable library version.