CVE-2026-42451

Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft

CVSS 6.3 MEDIUMEPSS 0.1%CWE-79 CWE-80

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.3EPSS 0.1%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

08 May 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

Affected products

grimmory-tools · grimmory

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References

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