CVE-2018-1121
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Description
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.
Statement
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.
Because an attacker can achieve similar results whether this vulnerability is present or not, Red Hat assesses its impact as Low.
Additional information
- Bugzilla 1575473: procps: process hiding through race condition enumerating /proc
- CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
- FAQ: Frequently asked questions about CVE-2018-1121
Common Vulnerability Scoring System (CVSS) Score Details
Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
Red Hat | NVD | |
---|---|---|
CVSS v3 Base Score | 3.9 | 5.9 |
Attack Vector | Local | Network |
Attack Complexity | Low | High |
Privileges Required | Low | None |
User Interaction | Required | None |
Scope | Unchanged | Unchanged |
Confidentiality Impact | None | None |
Integrity Impact | Low | High |
Availability Impact | Low | None |
CVSS v3 Vector
Red Hat: CVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L
NVD: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Acknowledgements
Red Hat would like to thank Qualys Research Labs for reporting this issue.
Frequently Asked Questions
Why is Red Hat's CVSS v3 score or Impact different from other vendors?
My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
What can I do if my product is listed as "Will not fix"?
What can I do if my product is listed as "Fix deferred"?
What is a mitigation?
I have a Red Hat product but it is not in the above list, is it affected?
Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?
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