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CVE-2026-42841 medium CVSS 4.8

Cross-Site Scripting (XSS) in getgrav/grav (CVE-2026-42841)

Summary

Cross-site scripting in getgrav/grav (CVE-2026-42841). Risk of unauthorized operations or information disclosure. Exploitable via onload. Mitigation: upgrade to 2.0.0-beta.2 or later.

Original description

The description as published by the source.

Summary

An authenticated user with page editing permissions can inject an executable JavaScript event-handler attribute into rendered image HTML through Grav's Markdown media action syntax.

The issue is caused by Markdown image query parameters being converted into callable media actions. The public attribute() media method can be reached this way, allowing an editor to set an arbitrary HTML attribute name and value on the generated image element.

For example, this Markdown:

![Quarterly market overview](market-overview.gif?attribute=onload,alert(document.domain))

is rendered as an image tag containing an executable onload handler:

This results in stored XSS when another user views the affected page. In a multi-user Grav installation, a lower-privileged page editor could use this to target administrators or reviewers who preview or view editor-controlled content.

Tested versions:

  • Grav CMS: 1.7.49.5
  • Admin Plugin: 1.10.49.1

Suggested classification:

  • CWE-79: Improper Neutralization of Input During Web Page Generation
  • Stored Cross-Site Scripting
  • Suggested CVSS v4.0 score if page editing is considered high privilege: 6.9 Medium
  • Suggested CVSS v4.0 vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
  • Suggested CVSS v3.1 score if page editing is considered high privilege: 6.9 Medium
  • Suggested CVSS v3.1 vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:L/A:N

Details

The issue appears to come from…

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-2026-42841 has been found in getgrav/grav.
Attackers can target a specific entry point like onload over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.8/10.
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-2026-42841" on the vendor's site.

CVE-2026-42841 (getgrav/grav) — CWE-79 / CVSS v3 4.8
Attack vector: remote (network-reachable)
Attack surface: onload / attribute / img / style
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.

❓ What is the problem

Cross-site scripting (XSS) (CWE-79) exists in getgrav/grav. Attackers reach the vulnerable code path via onload.

📍 Affected scope

Check the vendor advisory for the affected versions of getgrav/grav. Attack surface: onload / attribute / img / style.

🔥 Severity

Severity: Medium (CVSS 4.8/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.0.0-beta.2.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply 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。

  3. 3
    Post-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

composer getgrav/grav
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.0-beta.2"}]}]
Packagist getgrav/grav
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.0-beta.2"}]}]

References

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