{"uuid": "91b35345-8b5f-4e7a-825d-388dfea06514", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "GHSA-ffmg-hfvg-jhg9", "type": "seen", "source": "https://gist.github.com/alon710/9e473404cc3dda3bbd60707d9a5ddbdd", "content": "# CVE-2026-58657: CVE-2026-58657: Stored CSS Injection in Grav CMS Media Resize Parser\n\n> **CVSS Score:** 6.5\n> **Published:** 2026-09-16\n> **Full Report:** https://cvereports.com/reports/CVE-2026-58657\n\n## Summary\nCVE-2026-58657 is a critical stored CSS injection vulnerability in Grav CMS's media processing pipeline. By exploiting improper sanitization of image dimensions in the resize helper, low-privileged users with page editing permissions can inject arbitrary CSS styles. This can lead to visual defacement, UI redressing, and indirect data exfiltration.\n\n## TL;DR\nLow-privileged editors can inject arbitrary CSS via image resize query parameters due to missing type validation in Grav's media processing trait.\n\n## Technical Details\n\n- **CWE ID**: CWE-79\n- **Attack Vector**: Network\n- **CVSS Score**: 6.5\n- **EPSS Score**: 0.00371\n- **Impact**: Stored CSS Injection\n- **Exploit Status**: none\n- **KEV Status**: Not Listed\n\n## Affected Systems\n\n- Grav CMS\n- **Grav CMS**: < 2.0.0 (Fixed in: `2.0.0`)\n\n## Mitigation\n\n- Upgrade to Grav CMS version 2.0.0 or higher\n- Manually apply integer casting patch to StaticResizeTrait.php\n- Implement a restrictive Content Security Policy (CSP) for style-src\n\n**Remediation Steps:**\n1. Identify all Grav CMS instances running versions prior to 2.0.0\n2. Deploy the Grav 2.0.0 update via the admin dashboard or package manager\n3. Verify the fix by testing image markdown processing with non-numeric resize parameters\n4. Audit active page content for existing malformed markdown image references\n\n## References\n\n- [GitHub Security Advisory GHSA-ffmg-hfvg-jhg9](https://github.com/getgrav/grav/security/advisories/GHSA-ffmg-hfvg-jhg9)\n- [NVD - CVE-2026-58657](https://nvd.nist.gov/vuln/detail/CVE-2026-58657)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-58657) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-09-17T00:31:25.493497Z"}