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Unsafe defaults in `remark-html`

Critical severity GitHub Reviewed Published Sep 7, 2021 in remarkjs/remark-html • Updated Feb 1, 2023

Package

npm remark-html (npm)

Affected versions

< 13.0.2
= 14.0.0

Patched versions

13.0.2
14.0.1

Description

Impact

The documentation of remark-html has mentioned that it was safe by default. In practise the default was never safe and had to be opted into. This means arbitrary HTML can be passed through leading to potential XSS attacks.

Patches

The problem has been patched in 13.0.2 and 14.0.1: remark-html is now safe by default, and the implementation matches the documentation.

Workarounds

On older affected versions, pass sanitize: true, like so:

-  .use(remarkHtml)
+  .use(remarkHtml, {sanitize: true})

References

n/a

For more information

If you have any questions or comments about this advisory:

References

@wooorm wooorm published to remarkjs/remark-html Sep 7, 2021
Reviewed Sep 7, 2021
Published by the National Vulnerability Database Sep 7, 2021
Published to the GitHub Advisory Database Sep 7, 2021
Last updated Feb 1, 2023

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS score

0.089%
(39th percentile)

Weaknesses

CVE ID

CVE-2021-39199

GHSA ID

GHSA-9q5w-79cv-947m

Source code

Credits

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