Cross-Site Scripting (XSS) in getkirby/cms (CVE-2021-29460)
Summary
Cross-site scripting in getkirby/cms (CVE-2021-29460). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.5.4 or later.
Original description
The description as published by the source.
Kirby is an open source CMS. An editor with write access to the Kirby Panel can upload an SVG file that contains harmful content like `` tags. The direct link to that file can be sent to other users or visitors of the site. If the victim opens that link in a browser where they are logged in to Kirby, the script will run and can for example trigger requests to Kirby's API with the permissions of the victim. This vulnerability is critical if you might have potential attackers in your group of authenticated Panel users, as they can escalate their privileges if they get access to the Panel session of an admin user. Depending on your site, other JavaScript-powered attacks are possible. Visitors without Panel access can only use this attack vector if your site allows SVG file uploads in frontend forms and you don't already sanitize uploaded SVG files. The problem has been patched in Kirby 3.5.4. Please update to this or a later version to fix the vulnerability. Frontend upload forms need to be patched separately depending on how they store the uploaded file(s). If you use File::create(), you are protected by updating to 3.5.4+. As a work around you can disable the upload of SVG files in your file blueprints.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-29460 has been found in getkirby/cms.
Risk of unauthorized operations or information disclosure.
What to do: upgrade getkirby/cms to 3.5.4 or later.
If unsure, ask your IT team or search "getkirby/cms CVE-2021-29460" on the vendor's site.
CVE-2021-29460 (getkirby/cms) — CWE-79
Attack vector: remote (network-reachable)
Patched: 3.5.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Cross-site scripting (XSS) (CWE-79) exists in getkirby/cms.
Check the vendor advisory for the affected versions of getkirby/cms.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 3.5.4.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'getkirby/cms' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'getkirby/cms' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
getkirby/cmsを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade getkirby/cms to 3.5.4ステージング環境で 3.5.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- advisory github.com
- report github.com
- report packetstormsecurity.com