CVE-2020-28493
Description
A flaw was found in python-jinja2. The ReDOS vulnerability of the regex is mainly due to the sub-pattern [a-zA-Z0-9.-]+.[a-zA-Z0-9.-]+. This issue can be mitigated by Markdown to format user content instead of the urlize filter, or by implementing request timeouts and limiting process memory.
Statement
This flaw is out of support scope for the following products:
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Ceph Storage 2
To learn more about Red Hat Enterprise Linux support scopes, please see https://access.redhat.com/support/policy/updates/errata/
In Red Hat OpenStack Platform, because python-jinja2 is not directly customer exposed, the Impact has been moved to Low and no updated will be provided at this time for the RHOSP python-jinja2 package.
Red Hat Quay does not make use of the vulnerable function, so the impact is Low.
Mitigation
If using the jinja2 library as a developer, this flaw can be mitigated by not using the vulnerable urlize() filter, and instead, using Markdown to format user content.
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 | 7.5 | 5.3 | 5.3 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | Low | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P
Red Hat CVSS v3 Score Explanation
A:H because it could impact overall server system resources if limits are not set (worst case).
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU)
Attackers can create crafted inputs that intentionally cause the regular expression to use excessive backtracking in a way that causes the CPU consumption to spike.
Frequently Asked Questions
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