CVE-2026-42451

MEDIUMNVD 6.36.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.3 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 97% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
6.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
6.3
EG Score
6.3(medium)
EG Risk
28(Track)
EG Risk 28/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity63% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
3.5%
KEV
Not listed

Published

May 8, 2026

Last Modified

May 13, 2026

Advisory Details (2)

Auto-updated Jun 13, 2026
Patch available. Sources: github_release, github.
github Patch Available

Stored XSS via Malicious EPUB Enables Session Token Theft · Advisory · grimmory-tools/grimmory · GitHub

https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24
github_release Patch Available

Release v2.3.1

Patch available: grimmory-tools/grimmory v2.3.1

http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-24 14:17 UTCEPSS rescore
  2. 2026-07-23 14:18 UTCEPSS rescore
  3. 2026-07-23 03:11 UTCEG score recompute
  4. 2026-07-22 14:08 UTCEPSS rescore
  5. 2026-07-21 15:24 UTCEPSS rescore
  6. 2026-07-20 17:08 UTCEPSS rescore
  7. 2026-07-19 14:31 UTCEPSS rescore
  8. 2026-07-19 02:29 UTCEPSS rescore
  9. 2026-07-18 10:04 UTCEPSS rescore
  10. 2026-07-16 17:03 UTCEPSS rescore
  11. 2026-07-16 03:53 UTCOSV refresh
  12. 2026-07-15 16:57 UTCEPSS rescore
  13. 2026-07-15 02:00 UTCEPSS rescore
  14. 2026-07-13 22:30 UTCEPSS rescore
  15. 2026-07-13 06:13 UTCEPSS rescore
  16. 2026-07-12 05:46 UTCEPSS rescore
  17. 2026-07-11 08:27 UTCEPSS rescore
  18. 2026-07-09 19:10 UTCEPSS rescore
  19. 2026-07-08 15:15 UTCEPSS rescore
  20. 2026-07-07 13:46 UTCEPSS rescore
  21. 2026-07-06 02:23 UTCEPSS rescore
  22. 2026-07-06 02:23 UTCEPSS rescore
  23. 2026-07-05 02:30 UTCEPSS rescore
  24. 2026-07-04 06:31 UTCEPSS rescore
  25. 2026-07-01 15:06 UTCEPSS rescore
Show 57 more
  1. 2026-06-30 23:22 UTCEPSS rescore
  2. 2026-06-29 14:06 UTCEPSS rescore
  3. 2026-06-28 14:07 UTCEPSS rescore
  4. 2026-06-28 04:56 UTCEPSS rescore
  5. 2026-06-27 03:08 UTCEPSS rescore
  6. 2026-06-25 13:49 UTCEPSS rescore
  7. 2026-06-25 13:49 UTCEPSS rescore
  8. 2026-06-24 14:05 UTCEPSS rescore
  9. 2026-06-23 21:33 UTCEPSS rescore
  10. 2026-06-22 14:25 UTCEPSS rescore
  11. 2026-06-22 14:25 UTCEPSS rescore
  12. 2026-06-21 14:56 UTCEPSS rescore
  13. 2026-06-21 14:56 UTCEPSS rescore
  14. 2026-06-19 19:25 UTCEPSS rescore
  15. 2026-06-18 17:52 UTCEPSS rescore
  16. 2026-06-18 17:52 UTCEPSS rescore
  17. 2026-06-17 17:53 UTCEPSS rescore
  18. 2026-06-16 17:52 UTCEPSS rescore
  19. 2026-06-15 17:49 UTCEPSS rescore
  20. 2026-06-13 23:00 UTCEPSS rescore
  21. 2026-06-12 23:12 UTCEPSS rescore
  22. 2026-06-12 23:12 UTCEPSS rescore
  23. 2026-06-11 14:00 UTCEPSS rescore
  24. 2026-06-10 22:18 UTCEPSS rescore
  25. 2026-06-10 13:22 UTCEPSS rescore
  26. 2026-06-10 13:22 UTCEPSS rescore
  27. 2026-06-08 14:17 UTCEPSS rescore
  28. 2026-06-08 14:17 UTCEPSS rescore
  29. 2026-06-07 15:25 UTCEPSS rescore
  30. 2026-06-07 15:25 UTCEPSS rescore
  31. 2026-06-06 13:47 UTCEPSS rescore
  32. 2026-06-06 13:47 UTCEPSS rescore
  33. 2026-06-05 22:47 UTCEPSS rescore
  34. 2026-06-05 06:10 UTCEPSS rescore
  35. 2026-06-05 06:10 UTCEPSS rescore
  36. 2026-06-04 13:12 UTCEPSS rescore
  37. 2026-06-04 13:12 UTCEPSS rescore
  38. 2026-06-02 20:13 UTCEPSS rescore
  39. 2026-06-01 13:52 UTCEPSS rescore
  40. 2026-06-01 13:52 UTCEPSS rescore
  41. 2026-05-31 00:16 UTCEPSS rescore
  42. 2026-05-31 00:16 UTCEPSS rescore
  43. 2026-05-29 13:44 UTCEPSS rescore
  44. 2026-05-29 13:44 UTCEPSS rescore
  45. 2026-05-28 13:44 UTCEPSS rescore
  46. 2026-05-28 13:44 UTCEPSS rescore
  47. 2026-05-27 13:40 UTCEPSS rescore
  48. 2026-05-27 13:40 UTCEPSS rescore
  49. 2026-05-27 13:40 UTCEPSS rescore
  50. 2026-05-26 13:44 UTCEPSS rescore
  51. 2026-05-26 07:18 UTCEPSS rescore
  52. 2026-05-26 07:18 UTCEPSS rescore
  53. 2026-05-20 22:38 UTCEPSS rescore
  54. 2026-05-20 22:38 UTCEPSS rescore
  55. 2026-05-20 13:30 UTCEG score recompute
  56. 2026-05-20 11:22 UTCEPSS rescore
  57. 2026-05-20 11:22 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-42451?
CVE-2026-42451 is a medium vulnerability published on May 8, 2026. 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…
When was CVE-2026-42451 disclosed?
CVE-2026-42451 was first published in the National Vulnerability Database on May 8, 2026, with the most recent update on May 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42451 actively exploited?
CVE-2026-42451 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42451?
CVE-2026-42451 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2026-42451?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42451, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-42451

Explore →

Is Your Infrastructure Affected by CVE-2026-42451?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs