CVE-2019-25032 in Unbound
Summary
by MITRE • 04/27/2021
Unbound before 1.9.5 allows an integer overflow in the regional allocator via regional_alloc.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability CVE-2019-25032 represents a critical integer overflow flaw in the Unbound DNS resolver software version 1.9.5 and earlier. This issue specifically affects the regional allocator component, which is responsible for memory management within the DNS resolver's operational context. The regional allocator serves as a memory pool manager that handles dynamic allocation and deallocation of memory blocks during DNS query processing, making it a critical component in the overall security posture of the system.
The technical flaw manifests as an integer overflow condition within the regional_alloc function when processing certain memory allocation requests. This overflow occurs during the calculation of memory block sizes, where an attacker can manipulate input parameters to cause arithmetic overflow in the size calculation logic. When this overflow occurs, it results in a corrupted memory allocation that can lead to memory corruption, potentially allowing an attacker to overwrite adjacent memory locations with malicious data. The vulnerability stems from inadequate input validation and bounds checking within the memory allocation routine, where the system fails to properly validate that the calculated memory requirements remain within safe integer limits.
The operational impact of this vulnerability is significant as it can be exploited remotely through crafted DNS queries sent to the vulnerable Unbound resolver instance. An attacker who can influence the memory allocation process through DNS traffic can potentially trigger the integer overflow condition, leading to memory corruption that may result in arbitrary code execution or denial of service conditions. This makes the vulnerability particularly dangerous in network infrastructure environments where Unbound serves as a DNS resolver for critical services. The attack surface expands when considering that many organizations rely on Unbound for authoritative and recursive DNS services, making the potential impact widespread across networked environments.
Mitigation strategies for CVE-2019-25032 primarily focus on upgrading to Unbound version 1.9.5 or later, where the integer overflow vulnerability has been addressed through proper input validation and bounds checking mechanisms. System administrators should also implement network segmentation and access controls to limit exposure of vulnerable Unbound instances to untrusted networks. Additional protective measures include monitoring DNS traffic for anomalous patterns that might indicate exploitation attempts, implementing DNS security extensions, and maintaining regular security updates for all DNS resolver implementations. This vulnerability aligns with CWE-190, which describes integer overflow conditions, and falls under ATT&CK technique T1071.004 for application layer protocol usage in DNS communications, highlighting the need for comprehensive network security monitoring and defense in depth strategies to protect against such memory corruption vulnerabilities.