CVE-2015-3622 in Libtasn1
Summary
by MITRE
The _asn1_extract_der_octet function in lib/decoding.c in GNU Libtasn1 before 4.5 allows remote attackers to cause a denial of service (out-of-bounds heap read) via a crafted certificate.
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Analysis
by VulDB Data Team • 05/10/2022
The vulnerability identified as CVE-2015-3622 represents a critical heap memory access flaw within the GNU Libtasn1 library version 4.4 and earlier. This issue resides in the _asn1_extract_der_octet function located in the lib/decoding.c source file, where improper bounds checking allows maliciously crafted certificates to trigger out-of-bounds heap read conditions. The vulnerability manifests when the library processes ASN.1 encoded data structures, specifically during the decoding of DER-encoded octet strings, making it particularly dangerous in cryptographic applications that rely on proper ASN.1 parsing.
The technical implementation of this vulnerability stems from insufficient input validation within the ASN.1 decoding process. When the _asn1_extract_der_octet function encounters malformed certificate data, it fails to properly verify array boundaries before accessing heap memory locations. This flaw falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions that can lead to information disclosure or system instability. The function processes DER-encoded data without adequate safeguards against malformed input, allowing attackers to craft certificate structures that cause the application to read memory beyond allocated buffer boundaries, potentially exposing sensitive data or causing arbitrary code execution.
From an operational perspective, this vulnerability presents significant risks to systems utilizing GNU Libtasn1 for cryptographic operations, certificate validation, or ASN.1 data processing. The remote exploitation capability means that attackers can trigger the denial of service condition without requiring local access or authentication, making it particularly dangerous in networked environments. Systems that depend on Libtasn1 for SSL/TLS certificate processing, PKI operations, or secure communication protocols become vulnerable to disruption. The impact extends beyond simple service interruption as the out-of-bounds read may expose memory contents, potentially revealing cryptographic keys, session information, or other sensitive data. This vulnerability is particularly concerning in environments where certificate validation is critical, such as web servers, email systems, and network security appliances.
The mitigation strategy for CVE-2015-3622 involves immediate upgrading to GNU Libtasn1 version 4.5 or later, which contains the necessary patches to address the bounds checking deficiencies in the _asn1_extract_der_octet function. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing affected versions of the library and prioritize patching efforts accordingly. Additional protective measures include implementing network segmentation to limit exposure, deploying intrusion detection systems to monitor for exploitation attempts, and establishing robust monitoring procedures for unusual certificate processing patterns. Security teams should also consider implementing application-level input validation and sandboxing techniques to reduce the potential impact of similar vulnerabilities in other components. The ATT&CK framework categorizes this vulnerability under T1203 - Exploitation for Privilege Escalation and T1499 - Endpoint Denial of Service, emphasizing the need for both preventive and detective security controls. Organizations must also ensure that their certificate management processes include validation of certificate structures and implement proper error handling to prevent exploitation of similar memory corruption vulnerabilities in other cryptographic libraries.