Is CVE-2026-42451 in the CISA KEV catalog?

No. CVE-2026-42451 is not currently on the CISA Known Exploited Vulnerabilities list.

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

CVE-2026-42451 has a CVSS v3 base score of 6.3 (MEDIUM).

What is the EPSS score for CVE-2026-42451?

CVE-2026-42451 has an EPSS score of 0.14% (3th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2026-42451?

No published fix for CVE-2026-42451 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2026-42451

MEDIUM

6.3

CVSS v3

NVD

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.

CWE-79Cross-Site Scripting (XSS)CWE-80

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityHigh

Privileges RequiredLow

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityLow

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

Exploit Intelligence

0.14%probability of exploitation in 30 days

3rdpercentile

Low risk: more likely to be exploited than 3% of all known CVEs.

References

Other references2

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-13.