CVE-2021-42574
Description
A flaw was found in the way Unicode standards are implemented in the context of development environments, which have specialized requirements for rendering text. An attacker could exploit this to deceive a human reviewer by creating a malicious patch containing well placed BiDi characters. The special handling and rendering of those characters can be then used in an attempt to hide unexpected and potentially dangerous behaviour from the reviewer.
Security Bulletin
Statement
This is a flaw with the way Unicode standards are implemented in the context of development environments, which have specialized requirements for rendering text. This is not a flaw in Red Hat products.
Mitigation
This issue can be mitigated by ensuring code commits get a proper review. All new commits can also be scanned for the presence of BiDi characters before accepting the commit.
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 | 8.5 | 8.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | Required | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Application Data; Execute Unauthorized Code or Commands
An attacker could modify the structure of the message or data being sent to the downstream component, possibly injecting commands.
Acknowledgements
Red Hat would like to thank Nicholas Boucher and Ross Anderson (University of Cambridge) for reporting this issue.
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