CVE-2018-6003 in Libtasn1
Summary
by MITRE
An issue was discovered in the _asn1_decode_simple_ber function in decoding.c in GNU Libtasn1 before 4.13. Unlimited recursion in the BER decoder leads to stack exhaustion and DoS.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2018-6003 resides within the GNU Libtasn1 library, specifically in the _asn1_decode_simple_ber function located in decoding.c. This flaw represents a critical security issue that affects versions prior to 4.13 of the library. The vulnerability manifests as unlimited recursion during the Basic Encoding Rules (BER) decoding process, creating a condition where the stack memory becomes exhausted through recursive function calls. This type of vulnerability falls under the category of improper input validation and can be classified as CWE-674, which specifically addresses uncontrolled recursion within software systems. The root cause stems from the library's failure to properly implement recursion depth checking during the parsing of ASN.1 encoded data structures, particularly when processing malformed or specially crafted input sequences.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it creates a pathway for attackers to exploit the recursive nature of the decoder function. When an attacker crafts malicious ASN.1 data that triggers the vulnerable recursive behavior, the system's stack space rapidly depletes, leading to application crashes or complete system hangs. This vulnerability directly maps to ATT&CK technique T1499.004, which involves resource exhaustion attacks targeting application availability. The issue affects any application that relies on GNU Libtasn1 for ASN.1 parsing operations, including cryptographic applications, network protocols, and security infrastructure components that depend on proper ASN.1 decoding for certificate processing, protocol message handling, or data validation.
Mitigation strategies for CVE-2018-6003 primarily focus on immediate patching of the GNU Libtasn1 library to version 4.13 or later, which contains the necessary recursion depth controls and stack management improvements. Organizations should also implement input validation measures at the application level to sanitize ASN.1 data before processing, particularly when dealing with untrusted input sources. Network segmentation and monitoring solutions should be deployed to detect unusual patterns of resource consumption that might indicate exploitation attempts. Additionally, implementing stack overflow protection mechanisms and setting appropriate recursion limits within the application's ASN.1 processing code can provide additional defense layers. Security teams should conduct comprehensive vulnerability assessments to identify all systems utilizing GNU Libtasn1 and ensure proper patch management procedures are in place to prevent similar issues in other cryptographic libraries that may exhibit similar recursive decoding patterns. The vulnerability demonstrates the importance of proper stack management and input validation in cryptographic libraries, as these components often serve as foundational elements for security infrastructure and are prime targets for sophisticated exploitation attempts.