CVE-2019-11191 Explained : Impact and Mitigation

In versions of the Linux kernel up to 5.0.7, a vulnerability exists that allows local users to bypass ASLR on setuid a.out programs under specific configurations. The software maintainer disputes this as a vulnerability due to lack of ASLR support for a.out format executables.

Understanding CVE-2019-11191

This CVE highlights a potential security issue in the Linux kernel that could impact system security.

What is CVE-2019-11191?

CVE-2019-11191 is a vulnerability in the Linux kernel that enables local users to bypass ASLR on setuid a.out programs in certain system configurations.

The Impact of CVE-2019-11191

The vulnerability allows attackers to bypass ASLR, potentially leading to unauthorized access and exploitation of sensitive information on affected systems.

Technical Details of CVE-2019-11191

This section delves into the technical aspects of the CVE.

Vulnerability Description

The vulnerability arises due to a race condition in the load_aout_binary() function in fs/binfmt_aout.c, where the install_exec_creds() function is called too late, causing a race condition during the ptrace_may_access() check.

Affected Systems and Versions

Linux kernel versions up to 5.0.7
Systems configured with CONFIG_IA32_AOUT enabled and ia32_aout loaded

Exploitation Mechanism

The race condition occurs when reading the /proc/pid/stat file during the ptrace_may_access() check, allowing local users to bypass ASLR on setuid a.out programs.

Mitigation and Prevention

Protecting systems from CVE-2019-11191 requires immediate actions and long-term security practices.

Immediate Steps to Take

Disable CONFIG_IA32_AOUT if not required
Regularly monitor and update the Linux kernel to patched versions

Long-Term Security Practices

Implement least privilege access controls
Conduct regular security audits and vulnerability assessments

Patching and Updates

Apply relevant security patches provided by Linux distributions and vendors