CVE-2016-10197 in libevent
Summary
by MITRE
The search_make_new function in evdns.c in libevent before 2.1.6-beta allows attackers to cause a denial of service (out-of-bounds read) via an empty hostname.
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Analysis
by VulDB Data Team • 02/01/2025
The vulnerability identified as CVE-2016-10197 resides within the evdns.c component of the libevent library, specifically in the search_make_new function that handles DNS resolution operations. This flaw represents a classic out-of-bounds read vulnerability that can be exploited by malicious actors to disrupt service availability. The issue manifests when the function processes an empty hostname parameter, which occurs during DNS query handling within the event-driven networking framework. The libevent library serves as a fundamental networking component in numerous applications and systems, making this vulnerability particularly concerning from a security perspective.
The technical implementation of this vulnerability stems from inadequate input validation within the search_make_new function. When an empty hostname is passed to the function, the code fails to properly validate the input before attempting to access memory locations that may not be properly initialized or allocated. This results in the program attempting to read memory beyond the bounds of allocated buffers, causing unpredictable behavior and potentially leading to application crashes. The vulnerability specifically affects libevent versions prior to 2.1.6-beta, indicating that this was a known issue that was subsequently addressed in later releases. From a cybersecurity standpoint, this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions that can lead to denial of service or information disclosure.
The operational impact of CVE-2016-10197 extends beyond simple service disruption, as it can be leveraged in broader attack scenarios within the MITRE ATT&CK framework. An attacker could exploit this vulnerability to create persistent denial of service conditions against systems relying on libevent for DNS resolution, particularly in network infrastructure components, web servers, or applications that utilize event-driven networking patterns. The vulnerability's exploitation requires minimal prerequisites since it only requires sending a malformed DNS query with an empty hostname, making it particularly dangerous in environments where DNS services are exposed to untrusted networks. Systems that depend on libevent for asynchronous network operations, including those using HTTP servers, proxy services, and network monitoring tools, could be compromised through this vector.
Mitigation strategies for this vulnerability involve immediate patching of affected libevent installations to version 2.1.6-beta or later, which contains the necessary code modifications to properly validate hostname inputs. Organizations should also implement network-level controls to filter malformed DNS queries and monitor for unusual DNS traffic patterns that might indicate exploitation attempts. From a defensive perspective, this vulnerability underscores the importance of input validation in networking libraries and demonstrates how seemingly benign functions can become attack vectors when proper boundary checks are absent. Security teams should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable libevent versions and establish monitoring procedures to detect potential exploitation attempts, as the vulnerability can be used in combination with other attack vectors to create more sophisticated compromise scenarios.