CVE-2016-2053 in Android
Summary
by MITRE
The asn1_ber_decoder function in lib/asn1_decoder.c in the Linux kernel before 4.3 allows attackers to cause a denial of service (panic) via an ASN.1 BER file that lacks a public key, leading to mishandling by the public_key_verify_signature function in crypto/asymmetric_keys/public_key.c.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-2053 represents a critical denial of service weakness in the Linux kernel's handling of ASN.1 Basic Encoding Rules (BER) formatted data. This flaw exists within the cryptographic subsystem of the kernel, specifically in the asn1_ber_decoder function located in lib/asn1_decoder.c. The issue manifests when processing ASN.1 BER files that are missing public key components, creating a scenario where the kernel's public key verification mechanism fails catastrophically. The vulnerability operates at the intersection of cryptographic processing and kernel memory management, where improper input validation leads to system instability.
The technical implementation of this vulnerability stems from insufficient error handling within the kernel's asymmetric key processing pipeline. When the asn1_ber_decoder function encounters an ASN.1 BER structure lacking proper public key information, it fails to properly validate the input before passing control to the public_key_verify_signature function in crypto/asymmetric_keys/public_key.c. This function expects certain cryptographic parameters to be present and properly formatted, but receives malformed data that causes the kernel to panic and crash. The root cause aligns with CWE-248, which addresses improper exception handling in software systems, particularly in cryptographic contexts where malformed inputs can trigger system failures.
The operational impact of CVE-2016-2053 extends beyond simple system downtime, as it represents a potential vector for denial of service attacks against Linux systems that process ASN.1 encoded data. Systems utilizing kernel cryptographic services, particularly those handling certificate validation, secure communications, or digital signature verification, become vulnerable to exploitation. Attackers can craft malicious ASN.1 BER files that trigger the kernel panic, effectively causing the affected system to become unresponsive and requiring manual reboot. This vulnerability particularly affects systems that rely on kernel-level cryptographic operations for security functions, including those implementing secure boot processes, certificate validation, or cryptographic signature verification.
Mitigation strategies for CVE-2016-2053 primarily focus on applying the official kernel patch released with version 4.3, which includes enhanced input validation and proper error handling for ASN.1 BER processing. Organizations should prioritize kernel updates across all affected systems, particularly those handling cryptographic operations or processing external certificate data. Additional protective measures include implementing network segmentation to limit exposure to potentially malicious ASN.1 data sources, deploying intrusion detection systems to monitor for suspicious ASN.1 processing patterns, and establishing robust patch management procedures. From an ATT&CK framework perspective, this vulnerability maps to T1553.002 (Hijacking Execution Flow) and T1499.004 (Endpoint Denial of Service), as it represents a method for causing system instability through manipulation of cryptographic processing components. The vulnerability also aligns with T1068 (Exploitation for Privilege Escalation) as it could potentially be leveraged in more complex attack chains where system stability is compromised to facilitate further exploitation attempts.