CVE-2019-25039 in Unbound
Summary
by MITRE • 04/27/2021
Unbound before 1.9.5 allows an integer overflow in a size calculation in respip/respip.c.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability identified as CVE-2019-25039 represents a critical integer overflow flaw within the Unbound DNS resolver software version 1.9.5 and earlier. This issue manifests in the respip/respip.c source file where a size calculation routine fails to properly validate integer boundaries, creating a potential avenue for malicious exploitation. The vulnerability specifically affects the handling of response IP address data structures within the DNS resolution process, making it particularly dangerous in network infrastructure environments where DNS services are extensively utilized.
The technical implementation of this integer overflow occurs during the calculation of memory allocation sizes for response IP data structures. When processing DNS responses, the software performs arithmetic operations to determine the appropriate memory buffer size needed to store IP address information. The flaw arises because the calculation does not adequately check for integer overflow conditions, allowing an attacker to craft specially formatted DNS responses that trigger unexpected behavior in the memory allocation logic. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a fundamental weakness in software arithmetic operations.
The operational impact of CVE-2019-25039 extends beyond simple denial of service scenarios, potentially enabling more sophisticated attack vectors within DNS infrastructure. An attacker could leverage this vulnerability to cause memory corruption, leading to application crashes, unexpected behavior, or in severe cases, arbitrary code execution within the DNS resolver process. The vulnerability affects systems running Unbound versions prior to 1.9.5, making it particularly relevant for organizations maintaining older DNS resolver installations. This flaw represents a significant risk in enterprise environments where DNS servers serve as critical infrastructure components, potentially allowing attackers to disrupt network services or gain unauthorized access to sensitive information.
Mitigation strategies for this vulnerability primarily focus on immediate software updates to Unbound version 1.9.5 or later, which contains the necessary patches to address the integer overflow condition. Organizations should prioritize patching their DNS infrastructure components and conduct thorough testing to ensure compatibility with the updated software. Additional defensive measures include implementing network segmentation to limit exposure, monitoring DNS traffic for anomalous patterns, and establishing robust incident response procedures. The ATT&CK framework categorizes this vulnerability under the T1071.004 technique for application layer protocol usage, specifically DNS, highlighting the need for network monitoring and anomaly detection. System administrators should also consider implementing intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability, particularly in environments where DNS services are exposed to untrusted networks.