CVE-2020-1733
Description
A race condition flaw was found in Ansible Engine when running a playbook with an unprivileged become user. When Ansible needs to run a module with become user, the temporary directory is created in /var/tmp. This directory is created with "umask 77 && mkdir -p
Statement
Ansible Engine 2.7.16, 2.8.10, and 2.9.6 as well as previous versions are affected.
Ansible Tower 3.4.5, 3.5.5 and 3.6.3 as well as previous versions are affected.
In Red Hat OpenStack Platform, because the flaw has a lower impact, ansible is not directly customer exposed, and the fix would require a substantial amount of development, no update will be provided at this time for the RHOSP ansible package.
Mitigation
This issue can be mitigated by mounting the proc filesystem with hidepid=2 option (https://www.kernel.org/doc/Documentation/filesystems/proc.txt). This way only the user used by Ansible will be able to perform the attack as users on the system will be able to access only their processes /proc/$PID/ directories.
Also note that mounting proc filesystem with hidepid=2 might require re-mounting it on unpatched kernels, due to a kernel bug (see https://unix.stackexchange.com/questions/584054/why-procfs-mount-option-only-working-on-remount), there will be hidepid=3 in the future (https://patchwork.kernel.org/patch/11310217/).
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5 | 5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:L
NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:L
Understanding the Weakness (CWE)
Confidentiality,Integrity
Technical Impact: Read Files or Directories; Modify Files or Directories
Acknowledgements
Red Hat would like to thank Damien Aumaitre (Quarkslab) and Nicolas Surbayrole (Quarkslab) for reporting this issue.
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