CVE-2020-10030 in PowerDNS Recursor
Summary
by MITRE
An issue has been found in PowerDNS Recursor 4.1.0 up to and including 4.3.0. It allows an attacker (with enough privileges to change the system's hostname) to cause disclosure of uninitialized memory content via a stack-based out-of-bounds read. It only occurs on systems where gethostname() does not have '\0' termination of the returned string if the hostname is larger than the supplied buffer. (Linux systems are not affected because the buffer is always large enough. OpenBSD systems are not affected because the returned hostname always has '\0' termination.) Under some conditions, this issue can lead to the writing of one '\0' byte out-of-bounds on the stack, causing a denial of service or possibly arbitrary code execution.
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Analysis
by VulDB Data Team • 10/18/2020
The vulnerability identified as CVE-2020-10030 represents a critical memory safety issue affecting PowerDNS Recursor versions 4.1.0 through 4.3.0. This flaw stems from improper handling of hostname data during system enumeration processes, creating a potential vector for information disclosure and system compromise. The vulnerability specifically targets systems where the gethostname() function fails to properly null-terminate returned hostnames when the hostname exceeds the allocated buffer size, creating a dangerous condition that can be exploited by malicious actors with sufficient privileges to modify system hostnames. The issue manifests as a stack-based out-of-bounds read that can potentially result in uninitialized memory disclosure, making it particularly concerning for environments where sensitive data might be present in memory regions that become accessible through this vulnerability.
The technical implementation of this vulnerability involves a buffer management flaw in how PowerDNS Recursor processes hostname information obtained from system calls. When gethostname() returns a hostname that exceeds the expected buffer boundaries, the application fails to properly handle the truncation, leading to an out-of-bounds memory access pattern. This condition is particularly dangerous because it can result in a single null byte being written out-of-bounds on the stack, which creates a predictable memory corruption scenario. The vulnerability's exploitation potential is directly tied to the system's specific implementation of the gethostname() system call and the underlying operating system's memory management characteristics. This flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of improper boundary checking in memory management operations.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential system stability and security compromise. An attacker with sufficient privileges to modify system hostnames could potentially trigger the out-of-bounds write condition, leading to either denial of service through application crashes or more severe consequences including arbitrary code execution. The vulnerability's effectiveness is system-dependent, with Linux systems being inherently protected due to their larger buffer allocations and OpenBSD systems protected by guaranteed null termination, while other operating systems may be susceptible to this condition. This selective exposure creates a complex threat landscape where the vulnerability's impact varies significantly across different deployment environments, making comprehensive vulnerability assessment and mitigation challenging for security teams managing heterogeneous infrastructure.
Mitigation strategies for CVE-2020-10030 must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The primary recommendation involves upgrading PowerDNS Recursor to versions beyond 4.3.0 where this specific flaw has been addressed through proper buffer boundary checking and hostname handling mechanisms. Organizations should also implement monitoring for unauthorized hostname modifications and establish robust privilege controls to limit who can alter system configuration parameters. The vulnerability demonstrates the importance of adhering to secure coding practices as outlined in the ATT&CK framework's software development security domains, particularly focusing on preventing buffer overflows and ensuring proper memory management. Additionally, system administrators should consider implementing runtime protections such as stack canaries and address space layout randomization to reduce the exploitation potential even if the underlying vulnerability remains unpatched temporarily.