Is CVE-2026-42451 actively exploited?

No active exploitation of CVE-2026-42451 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-42451 be exploited remotely?

No. CVE-2026-42451 requires local access to exploit.

What is the CVSS score of CVE-2026-42451?

CVE-2026-42451 has a CVSS score of 6.3 (MEDIUM).

HOME VULNERABILITIESCVE-2026-42451

MEDIUM

CVE-2026-42451

CWE-79Published: May 8, 2026· Updated: May 13, 2026

6.3

CVSS v3.1

EPSS:0.01%probability of exploitation in 30 daysPercentile:0.7th

Official 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.

NVD Source

Technical Analysis

CVE-2026-42451 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), with a CVSS base score of 6.3.

From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.