What’s Vulnerable › Vulnerabilities

CVE-2026-42451: Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft

• Severity: medium (CVSS 6.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-08 · updated 2026-07-24
• Weakness: CWE-79

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.

Affected products

• grimmory-tools grimmory: before 2.3.1

References

• http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1
• https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24

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