CVE-2016-10151 in Hesiod
Summary
by MITRE
The hesiod_init function in lib/hesiod.c in Hesiod 3.2.1 compares EUID with UID to determine whether to use configurations from environment variables, which allows local users to gain privileges via the (1) HESIOD_CONFIG or (2) HES_DOMAIN environment variable and leveraging certain SUID/SGUID binary.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2016-10151 resides within the hesiod_init function located in lib/hesiod.c of the Hesiod 3.2.1 library implementation. This flaw represents a critical privilege escalation issue that affects systems utilizing the Hesiod name service resolution mechanism. Hesiod is a name service that provides access to DNS information through the traditional UNIX name service interface, commonly used for resolving hostnames and other network information. The vulnerability stems from a fundamental logic error in how the system determines when to process environment variables containing configuration data.
The technical flaw manifests in the hesiod_init function's improper comparison between the effective user ID (EUID) and the real user ID (UID) when deciding whether to utilize environment variables for configuration. This comparison logic is fundamentally flawed because it should typically validate that the effective user ID matches the real user ID to prevent privilege escalation scenarios. When the EUID and UID differ, it indicates that a setuid or setgid program is running, which should normally restrict the use of environment variables to prevent malicious exploitation. However, in this case, the function incorrectly allows the processing of environment variables even when running with elevated privileges, creating a path for local privilege escalation.
The operational impact of this vulnerability is severe and directly affects systems where Hesiod is integrated into network services or applications that utilize SUID/SGID binaries. Attackers can exploit this weakness by manipulating the HESIOD_CONFIG or HES_DOMAIN environment variables to inject malicious configuration data or domain information. When these variables are processed by a SUID/SGID binary that uses the vulnerable hesiod_init function, the attacker can effectively elevate their privileges to match those of the setuid/setgid program. This allows for unauthorized access to system resources and potential lateral movement within the network infrastructure.
The vulnerability aligns with CWE-276, which describes improper default permissions, and CWE-250, which addresses execution with unnecessary privileges. From an ATT&CK framework perspective, this represents a privilege escalation technique through environment variable manipulation, specifically categorized under T1068, which involves exploiting vulnerabilities in software to gain elevated privileges. The attack vector is particularly concerning because it requires no network access and can be executed locally, making it difficult to detect through traditional network monitoring tools.
Mitigation strategies for this vulnerability involve immediate patching of the Hesiod library to version 3.2.2 or later, which contains the corrected logic for environment variable processing. System administrators should also implement strict environment variable controls for SUID/SGID binaries, ensuring that these programs do not inherit potentially malicious environment settings. Additionally, monitoring for unauthorized changes to environment variables in processes that utilize Hesiod functionality should be implemented. The principle of least privilege should be enforced by reviewing and minimizing the use of SUID/SGID binaries where possible, as these present additional attack surfaces for exploitation. Organizations should also consider implementing runtime protection mechanisms that can detect and prevent the manipulation of critical environment variables in privileged contexts.