CVE-2016-8659 in Bubblewrap
Summary
by MITRE
Bubblewrap before 0.1.3 sets the PR_SET_DUMPABLE flag, which might allow local users to gain privileges by attaching to the process, as demonstrated by sending commands to a PrivSep socket.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2016-8659 affects bubblewrap versions prior to 0.1.3 and represents a privilege escalation flaw rooted in improper process security handling. Bubblewrap is a utility designed to create sandboxed environments for running applications with reduced privileges, commonly used in containerization and system isolation scenarios. The flaw manifests when the software sets the PR_SET_DUMPABLE flag during process execution, a mechanism that controls whether a process can be ptraced by other users or processes. This flag, when improperly configured, creates a security boundary that can be exploited by local attackers to gain elevated privileges.
The technical implementation of this vulnerability involves the manipulation of process attributes through the prctl system call, specifically the PR_SET_DUMPABLE flag which governs whether a process can be attached to by other users. When bubblewrap sets this flag inappropriately, it allows local users to attach debuggers or ptrace processes that should remain isolated. The exploitation occurs through a PrivSep socket mechanism where an attacker can send commands to the privileged process, effectively bypassing the intended sandbox boundaries. This attack vector leverages the fact that processes with PR_SET_DUMPABLE set can be monitored and controlled by users who do not normally have such access rights.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model that bubblewrap is designed to enforce. Local attackers can exploit this weakness to execute arbitrary code with elevated privileges, potentially leading to full system compromise. The vulnerability is particularly concerning in multi-user environments where sandboxed processes are expected to maintain strict isolation. Attackers can leverage this flaw to escalate privileges without requiring external network access or complex exploitation techniques, making it a significant concern for system administrators and security professionals managing containerized environments.
Mitigation strategies for CVE-2016-8659 focus on updating bubblewrap to version 0.1.3 or later, where the improper handling of the PR_SET_DUMPABLE flag has been corrected. System administrators should also implement additional security controls such as restricting access to ptrace capabilities through capabilities-based permissions or using mandatory access controls. The vulnerability aligns with CWE-276, which addresses improper privileges, and maps to ATT&CK technique T1068, which covers local privilege escalation through process manipulation. Organizations should also consider implementing process monitoring and anomaly detection to identify unauthorized ptrace activities that might indicate exploitation attempts. Additionally, the use of more restrictive security frameworks such as SELinux or AppArmor can provide additional layers of protection by limiting what processes can attach to others regardless of the PR_SET_DUMPABLE flag setting.