Cross-Site Scripting (XSS) in getgrav/grav (CVE-2026-42612)
Summary
Cross-site scripting in getgrav/grav (CVE-2026-42612). Confidential information can be exposed externally. Exploitable via onerror. Mitigation: upgrade to 2.0.0-beta.2 or later.
Original description
The description as published by the source.
Summary
A stored Cross-Site Scripting (XSS) vulnerability in getgrav/grav allows publisher-level accounts to execute arbitrary JavaScript. The issue arises from a blacklist bypass in the detectXss() function when handling unquoted HTML event attributes.
Details
The detectXss() function relies on a blacklist pattern to filter malicious attributes. The specific regex pattern used to match on* events is flawed:
'on_events' => '#(<[^>]+[a-z\x00-\x20\"\'\/])(on[a-z]+|xmlns)\s*=[\s|\'\"].*[\s|\'\"]>#iUu'
This pattern fails to properly identify on* event handlers that are constructed without quotation marks. This allows an attacker to completely bypass the filter. Note: It is highly recommended to replace this blacklist approach with a robust, established HTML sanitization library.
PoC
An attacker with publisher-level access can reproduce this by injecting the following payload into any vulnerable content field:
Execution Details:
The onerror event is written without quotes to bypass the regex. Because unquoted attributes are restricted in their character usage (e.g., the = symbol cannot be used easily), the payload leverages atob() and regex .source to decode the base64 string YWxlcnQoZG9jdW1lbnQuY29va2llKQ (which translates to alert(document.cookie)). The atob() function conveniently auto-completes the necessary = padding for the base64 string.
Impact
- Vulnerability Type: Stored Cross-Site Scripting (…
Source: NIST National Vulnerability Database NVD GitHub Advisory
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-2026-42612 has been found in getgrav/grav.
Attackers can target a specific entry point like onerror over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.5/10.
What to do: upgrade getgrav/grav to 2.0.0-beta.2 or later.
If unsure, ask your IT team or search "getgrav/grav CVE-2026-42612" on the vendor's site.
CVE-2026-42612 (getgrav/grav) — CWE-79 / CVSS v3 8.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: onerror / YWxlcnQoZG9jdW1lbnQuY29va2llKQ / on_events
Patched: 2.0.0-beta.2 — 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 getgrav/grav. Attackers reach the vulnerable code path via onerror.
Check the vendor advisory for the affected versions of getgrav/grav. Attack surface: onerror / YWxlcnQoZG9jdW1lbnQuY29va2llKQ / on_events.
Severity: High (CVSS 8.5/10). Confidential information can be exposed externally.
Update to 2.0.0-beta.2.
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 'getgrav/grav' . 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 'getgrav/grav' . | 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
getgrav/grav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 getgrav/grav to 2.0.0-beta.2ステージング環境で 2.0.0-beta.2 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。
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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
- package github.com
- web github.com
- web github.com
- web github.com