CVE-2017-9108 in adns
Summary
by MITRE
An issue was discovered in adns before 1.5.2. adnshost mishandles a missing final newline on a stdin read. It is wrong to increment used as well as setting r, since used is incremented according to r, later. Rather one should be doing what read() would have done. Without this fix, adnshost may read and process one byte beyond the buffer, perhaps crashing or perhaps somehow leaking the value of that byte.
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Analysis
by VulDB Data Team • 05/15/2023
The vulnerability identified as CVE-2017-9108 affects the adns library version 1.5.1 and earlier, specifically impacting the adnshost utility which is part of the asynchronous DNS resolution library. This flaw represents a classic buffer overflow condition that arises from improper handling of input data streams, particularly when processing standard input without proper newline termination. The issue manifests in the stdin reading mechanism where the software fails to correctly manage the relationship between read operations and buffer management, creating a scenario where memory boundaries are potentially violated.
The technical root cause of this vulnerability lies in the improper interaction between the read() system call and internal buffer tracking variables within the adnshost utility. When processing input from stdin, the code incorrectly increments both a used counter and a read result variable r, where the used variable is dependent on r's value. This creates a cascading effect where the program attempts to process data beyond the intended buffer boundaries, effectively reading one additional byte beyond the allocated memory space. The vulnerability stems from a fundamental misunderstanding of how to properly track and manage input buffer consumption, leading to undefined behavior that can manifest as memory corruption or information disclosure.
The operational impact of this vulnerability extends beyond simple program crashes, potentially enabling attackers to exploit the buffer over-read condition for more sophisticated attacks. When adnshost encounters input without a final newline, the improper increment logic causes it to access memory locations that should remain untouched, potentially exposing sensitive data from adjacent memory regions. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and more specifically with CWE-787, representing out-of-bounds write operations. The vulnerability can be leveraged in scenarios where an attacker controls the stdin input, potentially allowing for information leakage or in some cases, code execution depending on the memory layout and surrounding data.
From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and information gathering through memory corruption. The flaw can be exploited as part of a broader attack chain where initial access is achieved through other means, and this vulnerability serves as a mechanism for information disclosure or further privilege escalation. The vulnerability's impact is particularly concerning in environments where adnshost is used in automated systems or as part of larger network infrastructure, as it could be exploited by attackers to gain insights into system memory or potentially disrupt services through controlled crashes. The fix for this vulnerability required correcting the buffer management logic to ensure that only the actual read operations are properly tracked, eliminating the double increment that led to the overflow condition.
The remediation approach for CVE-2017-9108 involves updating to adns version 1.5.2 or later, where the buffer handling logic has been corrected to properly manage the relationship between read operations and buffer tracking variables. Security practitioners should prioritize this update across all systems where adnshost is deployed, particularly in server environments or automated systems that process external input through stdin. Organizations should also implement monitoring for any unusual behavior in systems running affected versions, as the vulnerability's exploitation could result in subtle memory corruption that might not immediately manifest as a crash but could lead to data leakage over time. The fix demonstrates the importance of proper input validation and buffer management in network utilities, emphasizing the need for thorough testing of edge cases including malformed input conditions.