CVE-2017-9772 in Compiler
Summary
by MITRE
Insufficient sanitisation in the OCaml compiler versions 4.04.0 and 4.04.1 allows external code to be executed with raised privilege in binaries marked as setuid, by setting the CAML_CPLUGINS, CAML_NATIVE_CPLUGINS, or CAML_BYTE_CPLUGINS environment variable.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 12/29/2020
The vulnerability identified as CVE-2017-9772 represents a critical security flaw in the OCaml compiler ecosystem affecting versions 4.04.0 and 4.04.1. This issue stems from inadequate input sanitization mechanisms within the compiler's handling of environment variables, specifically those related to plugin loading paths. The flaw enables malicious actors to escalate privileges when executing setuid binaries that utilize OCaml's compilation capabilities, creating a significant vector for privilege escalation attacks. The vulnerability operates by manipulating environment variables that control plugin discovery and loading processes, which are typically used to extend compiler functionality through external modules.
The technical root cause of this vulnerability lies in the compiler's failure to properly validate or sanitize environment variable inputs before processing them during the compilation process. When the OCaml compiler encounters the CAML_CPLUGINS, CAML_NATIVE_CPLUGINS, or CAML_BYTE_CPLUGINS environment variables, it directly incorporates their values into the plugin loading mechanism without adequate sanitization checks. This design flaw allows attackers to inject malicious paths or commands through these environment variables, potentially causing the compiler to load and execute unauthorized code with elevated privileges. The vulnerability specifically impacts binaries marked as setuid, where the effective user ID is elevated to root or another privileged account, making the exploitation particularly dangerous.
The operational impact of CVE-2017-9772 extends beyond simple privilege escalation, as it can enable attackers to gain unauthorized access to system resources and potentially compromise entire systems. When setuid binaries compiled with vulnerable OCaml versions are executed, the attacker-controlled environment variables can cause the compiler to load malicious plugins from arbitrary locations, effectively bypassing normal security controls. This vulnerability affects systems where OCaml is used for compiling applications that may be invoked with elevated privileges, particularly in environments where system administrators rely on setuid binaries for legitimate administrative functions. The implications are severe as attackers can leverage this flaw to execute arbitrary code with the privileges of the setuid process owner, potentially leading to complete system compromise.
Mitigation strategies for CVE-2017-9772 primarily focus on updating to patched versions of the OCaml compiler where the sanitization issues have been addressed. System administrators should immediately upgrade to OCaml version 4.04.2 or later, which contains the necessary fixes for environment variable validation. Additionally, organizations should implement strict environment variable controls by removing or restricting the use of the affected environment variables in setuid contexts, particularly when these variables are not essential for legitimate compiler operations. The principle of least privilege should be enforced by avoiding the use of setuid binaries where possible, and implementing proper input validation mechanisms that prevent arbitrary environment variable injection. This vulnerability aligns with CWE-77 and CWE-20 categories related to improper neutralization of special elements and input validation failures, and it maps to ATT&CK techniques involving privilege escalation through environment variable manipulation and compiler-based attacks.