CVE-2021-29503
Improper Neutralization of Script-Related HTML Tags in Notes
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
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.
Timeline
ID reserved
By GitHub_M
- 50 days later
· 50 days later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
- EPSS (exploitation in 30 days)
- 1.0% · top 36% of all CVEs (7 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.1.
Weakness
Affected products
References (3)
- https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-gjg7-4j2h-94fq (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/hedgedoc/hedgedoc/commit/01dad5821ee28377ebe640c6c72c3e0bb0d51ea7 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/hedgedoc/hedgedoc/releases/tag/1.8.2 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-29503)Record last updated .