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VulnerabilityPublished Updated

CVE-2026-42451: grimmory · Cross-site Scripting

Affects grimmorySource CVE Database V5

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Not known to be exploited · CVSS 6.3 Medium : upgrade to 2.3.1 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.3.1
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade grimmory and grimmory-tools/grimmory to 2.3.1.

Affected software

ProductAffectedFixed in
grimmory-toolsgrimmoryAffected
  • <2.3.1
Fixed in
  • 2.3.1
GitHubgrimmory-tools/grimmorypkg:github/grimmory-tools/grimmoryOther threatsAffected
  • <2.3.1
Fixed in
  • 2.3.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Grimmory to version 2.3.1 or later, where this vulnerability has been patched. No other mitigations are specified or required once the update is applied.

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.

References

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