Vulnerability Details : CVE-2021-29503
HedgeDoc is a platform to write and share markdown. HedgeDoc before version 1.8.2 is vulnerable to a cross-site scripting attack using the YAML-metadata of a note. An attacker with write access to a note can embed HTML tags in the Open Graph metadata section of the note, resulting in the frontend rendering the script tag as part of the `<head>` section. Unless your instance prevents guests from editing notes, this vulnerability allows unauthenticated attackers to inject JavaScript into notes that allow guest edits. If your instance prevents guests from editing notes, this vulnerability allows authenticated attackers to inject JavaScript into any note pages they have write-access to. This vulnerability is patched in version 1.8.2. As a workaround, one can disable guest edits until the next update.
Vulnerability category: Cross site scripting (XSS)
Products affected by CVE-2021-29503
- cpe:2.3:a:hedgedoc:hedgedoc:*:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-29503
1.89%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 82 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-29503
| Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
|---|---|---|---|---|---|---|
|
4.3
|
MEDIUM | AV:N/AC:M/Au:N/C:N/I:P/A:N |
8.6
|
2.9
|
NIST | |
|
6.1
|
MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
2.8
|
2.7
|
NIST | |
|
8.1
|
HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N |
2.8
|
5.2
|
GitHub, Inc. |
CWE ids for CVE-2021-29503
-
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.Assigned by: nvd@nist.gov (Primary)
-
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.Assigned by: security-advisories@github.com (Secondary)
References for CVE-2021-29503
-
https://github.com/hedgedoc/hedgedoc/commit/01dad5821ee28377ebe640c6c72c3e0bb0d51ea7
Merge pull request from GHSA-gjg7-4j2h-94fq · hedgedoc/hedgedoc@01dad58 · GitHubPatch;Third Party Advisory
-
https://github.com/hedgedoc/hedgedoc/releases/tag/1.8.2
Release HedgeDoc 1.8.2 · hedgedoc/hedgedoc · GitHubThird Party Advisory
-
https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-gjg7-4j2h-94fq
Improper Neutralization of Script-Related HTML Tags in Notes · Advisory · hedgedoc/hedgedoc · GitHubPatch;Third Party Advisory
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