CVE-2021-41258
Cross-site scripting (XSS) from image block content in the site frontend
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
Kirby is an open source file structured CMS. In affected versions Kirby's blocks field stores structured data for each block. This data is then used in block snippets to convert the blocks to HTML for use in your templates. We recommend to escape HTML special characters to protect against cross-site scripting (XSS) attacks. The default snippet for the image block unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. Attackers must be in your group of authenticated Panel users in order to exploit this weakness. Users who do not make use of the blocks field are not affected. This issue has been patched in Kirby version 3.5.8 by escaping special HTML characters in the output from the default image block snippet. Please update to this or a later version to fix the vulnerability.
Timeline
ID reserved
By GitHub_M
- 2 months later
· 2 months 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 | High7.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.81% · top 43% of all CVEs (7 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.3.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Packagistgetkirby/cmsGHSA-cq58-r77c-5jjw (opens in a new tab)
References (3)
- https://github.com/getkirby/kirby/releases/tag/3.5.8 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/getkirby/kirby/security/advisories/GHSA-cq58-r77c-5jjw (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/getkirby/kirby/pull/3510 (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 Advisory GHSA-cq58-r77c-5jjw (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-2021-41258)Record last updated .