GHSA-vfrc-7r7c-w9mx

    Dashboard / Vulnerabilities / GHSA-vfrc-7r7c-w9mx

    GHSA-vfrc-7r7c-w9mx

    Published: 24 Nov 2020Last Modified: 8 Jul 2026

    Summary: Prototype Pollution in highlight.js

    Details: ### Impact Affected versions of this package are vulnerable to Prototype Pollution. A malicious HTML code block can be crafted that will result in prototype pollution of the base object's prototype during highlighting. If you allow users to insert custom HTML code blocks into your page/app via parsing Markdown code blocks (or similar) and do not filter the language names the user can provide you may be vulnerable. The pollution should just be harmless data but this can cause problems for applications not expecting these properties to exist and can result in strange behavior or application crashes, i.e. a potential DOS vector. _If your website or application does not render user provided data it should be unaffected._ ### Patches Versions 9.18.2 and 10.1.2 and newer include fixes for this vulnerability. If you are using version 7 or 8 you are encouraged to upgrade to a newer release. ### Workarounds #### Patch your library Manually patch your library to create null objects for both `languages` and `aliases`: ```js const HLJS = function(hljs) { // ... var languages = Object.create(null); var aliases = Object.create(null); ``` #### Filter out bad data from end users: Filter the language names that users are allowed to inject into your HTML to guarantee they are valid. ### References * [What is Prototype Pollution?](https://codeburst.io/what-is-prototype-pollution-49482fc4b638) * https://github.com/highlightjs/highlight.js/pull/2636 ### For more information If you have any questions or comments about this advisory: * Please file an issue against [highlight.js](https://github.com/highlightjs/highlight.js/issues/)

    References: https://github.com/highlightjs/highlight.js/security/advisories/GHSA-vfrc-7r7c-w9mx, https://nvd.nist.gov/vuln/detail/CVE-2020-26237, https://github.com/highlightjs/highlight.js/pull/2636, https://github.com/highlightjs/highlight.js/commit/7241013ae011a585983e176ddc0489a7a52f6bb0, https://github.com/highlightjs/highlight.js, https://lists.debian.org/debian-lts-announce/2020/12/msg00041.html, https://www.npmjs.com/package/highlight.js, https://www.oracle.com/security-alerts/cpujul2022.html

    Affected packages

    Package

    Name: highlight.js

    Purl: pkg:npm/highlight.js

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -9.18.2

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    GHSA-vfrc-7r7c-w9mx | CVE-DB