CVE-2021-3997
Description
A flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.
Statement
Red Hat Enterprise Linux 8 has a default 1024 nofile limit, thus preventing systemd-tmpfiles from exhausting its stack and crashing. For this reason, this flaw has been rated as having a security impact of Low on Red Hat Enterprise Linux 8. For more information on default ulimit values, please see https://access.redhat.com/solutions/4482841.
The systemd version of Red Hat Enterprise Linux 9 is not affected by this issue, as the fix was back ported to it when the systemd package was rebased for upstream's v250 version on RHBA-2022:3979.
In OpenShift Container Platform (OCP) systemd package was shipped with OCP 4.7 as a one-off instance and all the later OCP releases (4.8, 4.9) are using systemd from RHEL 8. Hence, the systemd package shipped with OCP 4.7 will not be fixed and the fix will be consumed from RHEL 8.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Resources including CPU, memory, and stack memory could be rapidly consumed or exhausted, eventually leading to an exit or crash.
Confidentiality
Technical Impact: Read Application Data
In some cases, an application's interpreter might kill a process or thread that appears to be consuming too much resources, such as with PHP's memory_limit setting. When the interpreter kills the process/thread, it might report an error containing detailed information such as the application's installation path.
Acknowledgements
Red Hat would like to thank Qualys Research Labs for reporting this issue.
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