CVE-2026-42451

Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft

State: Published
Severity: 6.3 Medium
Published: May 8, 2026
Updated: May 12, 2026
Reserved: Apr 27, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	6.3 Medium	CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

Affected Products

Product	Versions
grimmorygrimmory-tools	< 2.3.1Affected

References

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