CVE-2016-10195 in libevent
Summary
by MITRE
The name_parse function in evdns.c in libevent before 2.1.6-beta allows remote attackers to have unspecified impact via vectors involving the label_len variable, which triggers an out-of-bounds stack read.
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Analysis
by VulDB Data Team • 09/08/2020
The vulnerability identified as CVE-2016-10195 affects the libevent library version 2.1.6-beta and earlier, specifically within the evdns.c file where the name_parse function processes DNS name parsing operations. This flaw represents a critical security issue that enables remote attackers to exploit an out-of-bounds stack read condition through manipulation of the label_len variable during DNS resolution processes. The vulnerability arises from insufficient input validation and boundary checking within the DNS name parsing logic, creating a scenario where maliciously crafted DNS responses can trigger memory access violations.
The technical implementation of this vulnerability stems from improper handling of DNS label length parameters during the name parsing phase of DNS resolution. When the name_parse function processes DNS names, it fails to adequately validate the label_len variable against expected bounds, allowing attackers to craft DNS responses that contain malformed label lengths. This results in the function reading beyond allocated stack memory boundaries, potentially exposing sensitive data or enabling further exploitation techniques. The flaw operates at the network protocol processing layer where DNS name resolution occurs, making it particularly dangerous as it can be triggered during normal network operations without requiring special privileges or user interaction.
From an operational perspective, this vulnerability can have significant impact on systems utilizing libevent for DNS resolution, particularly in environments where untrusted DNS responses are processed. The out-of-bounds read condition may lead to information disclosure, application crashes, or potentially more severe consequences depending on the specific memory layout and system configuration. Attackers can exploit this vulnerability by sending specially crafted DNS responses to systems running vulnerable libevent versions, causing the name_parse function to access invalid memory locations. The unspecified impact mentioned in the CVE description suggests that the consequences could vary based on system memory layout and could potentially be leveraged for privilege escalation or denial of service attacks.
The vulnerability aligns with CWE-129, which addresses insufficient validation of length fields, and represents a classic example of improper input validation in network protocol handlers. According to ATT&CK framework, this vulnerability could be categorized under T1059.007 for DNS resolution manipulation and potentially T1499 for network denial of service attacks. Organizations should prioritize immediate patching of affected systems to address this vulnerability, as the out-of-bounds read condition creates opportunities for information disclosure and system instability. The recommended mitigation strategy involves upgrading to libevent version 2.1.6-beta or later, which includes proper bounds checking for the label_len variable and enhanced validation of DNS name parsing operations. Additionally, network monitoring should be implemented to detect anomalous DNS traffic patterns that might indicate exploitation attempts, and system hardening measures should be applied to limit the impact of potential exploitation through stack canaries and address space layout randomization.