CVE-2021-41252

HIGHNVD 7.37.3—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.3 under NVD CVSS v3. EPSS exploit probability: 0.8%, top 26% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.3
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
7.3
EG Score
7.3(medium)
EPSS
55.4%
KEV
Not listed

Published

November 16, 2021

Last Modified

November 21, 2024

References (6)

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
getkirby/cms3.5.0 ... 3.5.7.1 (15 versions)3.5.8—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-11 08:25 UTCEPSS rescore
  2. 2026-07-11 08:25 UTCEPSS rescore
  3. 2026-07-09 19:07 UTCEPSS rescore
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  16. 2026-06-30 23:20 UTCEPSS rescore
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  18. 2026-06-30 05:30 UTCOSV refresh
  19. 2026-06-29 14:04 UTCEPSS rescore
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  1. 2026-06-25 13:48 UTCEPSS rescore
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  8. 2026-06-21 01:58 UTCEPSS rescore
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  10. 2026-06-19 19:24 UTCEPSS rescore
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  22. 2026-06-13 22:58 UTCEPSS rescore
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  24. 2026-06-12 23:10 UTCEPSS rescore
  25. 2026-06-12 16:40 UTCOSV refresh
  26. 2026-06-11 13:58 UTCEPSS rescore
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  28. 2026-06-10 22:16 UTCEPSS rescore
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  42. 2026-06-02 20:11 UTCEPSS rescore
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  44. 2026-06-01 13:50 UTCEPSS rescore
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  46. 2026-05-31 22:29 UTCEPSS rescore
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  48. 2026-05-31 00:15 UTCEPSS rescore
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  50. 2026-05-29 13:42 UTCEPSS rescore
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  57. 2026-05-26 07:30 UTCEG score recompute
  58. 2026-05-26 07:17 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-41252?
CVE-2021-41252 is a high vulnerability published on November 16, 2021. 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…
When was CVE-2021-41252 disclosed?
CVE-2021-41252 was first published in the National Vulnerability Database on November 16, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-41252 actively exploited?
CVE-2021-41252 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 55.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-41252?
CVE-2021-41252 has a CVSS v3 base score of 7.3 (NVD).
How do I remediate CVE-2021-41252?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-41252, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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