CVE-2015-5726 in Botan
Summary
by MITRE
The BER decoder in Botan 0.10.x before 1.10.10 and 1.11.x before 1.11.19 allows remote attackers to cause a denial of service (application crash) via an empty BIT STRING in ASN.1 data.
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Analysis
by VulDB Data Team • 11/26/2018
The vulnerability identified as CVE-2015-5726 represents a critical denial of service flaw within the Botan cryptographic library implementation. This issue specifically affects versions 0.10.x prior to 1.10.10 and 1.11.x prior to 1.11.19, where the Basic Encoding Rules (BER) decoder fails to properly handle certain malformed ASN.1 data structures. The flaw manifests when the decoder encounters an empty BIT STRING within ASN.1 formatted data, causing the application to crash and potentially leading to service disruption. This vulnerability operates at the intersection of ASN.1 parsing and cryptographic library security, where improper input validation leads to application instability.
The technical root cause of this vulnerability lies in the BER decoder's inadequate handling of edge cases within ASN.1 data structures. When processing an empty BIT STRING, the decoder does not properly validate the data structure before attempting to parse it, resulting in a null pointer dereference or similar memory access violation. This type of flaw falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions that can lead to application crashes and potential information disclosure. The vulnerability is particularly dangerous because it can be triggered through network-based attacks where malicious actors send specially crafted ASN.1 data to systems using vulnerable Botan versions, making it a prime target for remote exploitation.
The operational impact of CVE-2015-5726 extends beyond simple service disruption to potentially compromise the availability of cryptographic services within affected systems. Applications that rely on Botan for SSL/TLS operations, certificate processing, or cryptographic protocol implementations become vulnerable to denial of service attacks that can render them unavailable to legitimate users. This vulnerability directly maps to the ATT&CK technique T1499.004 which involves network denial of service attacks, and represents a critical weakness in the cryptographic infrastructure layer. Systems using vulnerable Botan versions may experience cascading failures when the application crashes, potentially affecting multiple services that depend on secure communication protocols.
Mitigation strategies for this vulnerability require immediate patching of affected Botan library versions to the fixed releases 1.10.10 and 1.11.19 respectively. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable Botan versions and prioritize remediation efforts accordingly. Additionally, network-level protections such as input validation at firewalls and intrusion detection systems can provide temporary defense against exploitation attempts. The vulnerability demonstrates the importance of robust input validation in cryptographic libraries and highlights the need for comprehensive testing of edge cases in ASN.1 parsing implementations. Security monitoring should include detection of unusual network traffic patterns that might indicate exploitation attempts targeting this specific vulnerability.