CVE-2019-13272

Published: 17 July 2019

In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to create a ptrace relationship, which allows local users to obtain root access by leveraging certain scenarios with a parent-child process relationship, where a parent drops privileges and calls execve (potentially allowing control by an attacker). One contributing factor is an object lifetime issue (which can also cause a panic). Another contributing factor is incorrect marking of a ptrace relationship as privileged, which is exploitable through (for example) Polkit's pkexec helper with PTRACE_TRACEME. NOTE: SELinux deny_ptrace might be a usable workaround in some environments.

From the Ubuntu Security Team

Jann Horn discovered that the ptrace implementation in the Linux kernel did not properly record credentials in some situations. A local attacker could use this to cause a denial of service (system crash) or possibly gain administrative privileges.

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-13272
• http://packetstormsecurity.com/files/153663/Linux-PTRACE_TRACEME-Broken-Permission-Object-Lifetime-Handling.html
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6994eefb0053799d2e07cd140df6c2ea106c41ee
• https://ubuntu.com/security/notices/USN-4093-1
• https://ubuntu.com/security/notices/USN-4094-1
• https://ubuntu.com/security/notices/USN-4095-1
• https://ubuntu.com/security/notices/USN-4117-1
• https://ubuntu.com/security/notices/USN-4118-1
• NVD
• Launchpad
• Debian

Bugs

• https://bugs.chromium.org/p/project-zero/issues/detail?id=1903
• https://bugzilla.redhat.com/show_bug.cgi?id=1730895
• https://bugzilla.suse.com/show_bug.cgi?id=1140671