CVE-2021-41252
No exploitation reported by the sources we read.
- Published2021-11-16
- Fixed in3.5.8
- WeaknessCWE-79
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
Kirby is an open source file structured CMS ### Impact Kirby's writer field stores its formatted content as HTML code. Unlike with other field types, it is not possible to escape HTML special characters against cross-site scripting (XSS) attacks, otherwise the formatting would be lost. If the user is logged in to the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim. Because the writer field did not securely sanitize its contents on save, it was possible to inject malicious HTML code into the content file by sending it to Kirby's API directly without using the Panel. This malicious HTML code 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 writer field are not affected. This issue has been patched in Kirby 3.5.8 by sanitizing all writer field contents on the backend whenever the content is modified via Kirby's API. Please update to this or a later version to fix the vulnerability.
Timeline
dates in UTC- 2021-11-1618:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-41252?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-41252?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
OSV · NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.5 | ≥ 3.5.0, < 3.5.8 | 3.5.8 | OSV |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.5 | ≥ 3.5.0, ≤ 3.5.7.1 | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
- Update getkirby/cms to 3.5.8
Advisories and patches
- github.comPatch
- github.comRelease Notes
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- Published
- 2021-11-16
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-41252?
Is CVE-2021-41252 actively exploited?
What is the CVSS score for CVE-2021-41252?
Running getkirby/cms? Hear about its next vulnerability
Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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