Since the kernel's proc_pid_readdir() returns PID entries in ascending numeric order, a process occupying a high PID can use inotify events to determine when the process list is being scanned, and fork/exec to obtain a lower PID, thus avoiding enumeration. An unprivileged attacker can hide a process from procps-ng's utilities by exploiting a race condition in reading /proc/PID entries.
Find out more about CVE-2018-1121 from the MITRE CVE dictionary dictionary and NIST NVD.
The /proc filesystem is not a reliable mechanism to account for processes running on a system, as it is unable to offer snapshot semantics. Short-lived processes have always been able to escape detection by tools that monitor /proc. This CVE simply identifies a reliable way to do so using inotify.
Process accounting for security purposes, or with a requirement to record very short-running processes and those attempting to evade detection, should be performed with more robust methods such as auditd(8) (the Linux Audit Daemon) or systemtap.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 3.9 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L |
| Attack Vector | Local |
| Attack Complexity | Low |
| Privileges Required | Low |
| User Interaction | Required |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity Impact | Low |
| Availability Impact | Low |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 7 | procps-ng | Will not fix |
| Red Hat Enterprise Linux 6 | procps | Will not fix |
| Red Hat Enterprise Linux 5 | procps | Will not fix |
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