CVE-2020-8131
Description
An arbitrary file write flaw was found in Yarn. This flaw allows an attacker to write files to a user’s system in unexpected places, potentially leading to remote code execution. The attacker would need to first trick a developer into installing a malicious package.
Statement
Normally yarn allows packages to run postinstall scripts which can write arbitrary files to the users system. This vulnerability allows an attacker to better hide the attack and also allow arbitrary file write when postinstall scripts are disabled with the '--ignore-scripts' option of 'yarn install'.
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 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | 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:N/UI:R/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
Since a user would have to be using the --ignore-scripts feature of 'yarn install' that's a configuration option beyond the attacker's control, making the access complexity metric high. Also, the attacker would have to trick a user into actually installing their malicious yarn package, making user interaction required.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If a malicious user injects a character (such as a semi-colon) that delimits the end of one command and the beginning of another, it may be possible to then insert an entirely new and unrelated command that was not intended to be executed. This gives an attacker a privilege or capability that they would not otherwise have.
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