CVE-2026-8391

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-05-12. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
21.6%
KEV
Not listed

Published

May 12, 2026

Last Modified

June 30, 2026

Advisory Details (5)

Auto-updated Jun 16, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-51/
generic

Security Vulnerabilities fixed in Firefox ESR 140.11 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-48/
generic

Security Vulnerabilities fixed in Firefox ESR 115.36 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-47/
generic

Security Vulnerabilities fixed in Firefox 150.0.3 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-45/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2038575

Vendor Advisories for CVE-2026-8391(20)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(21)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatfirefox-0:140.11.0-1.el10_02026-06-22redhat
redhatfirefox-0:140.11.0-1.el8_82026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_62026-06-17redhat
redhatthunderbird-0:140.11.0-1.el10_02026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_22026-06-17redhat
redhatthunderbird-0:140.11.0-1.el9_62026-06-17redhat
redhatfirefox-0:140.11.0-1.el9_42026-06-17redhat
redhatfirefox-0:140.11.0-1.el7_92026-06-17redhat
redhatfirefox-0:140.11.0-1.el8_42026-06-17redhat
redhatthunderbird-0:140.11.0-1.el8_82026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el9_42026-06-16redhat
redhatthunderbird-0:140.11.0-1.el9_22026-06-16redhat
redhatthunderbird-0:140.11.0-1.el8_102026-06-03redhat
redhatthunderbird-0:140.11.0-1.el10_22026-06-01redhat
redhatthunderbird-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el9_82026-05-27redhat
redhatfirefox-0:140.11.0-1.el8_102026-05-27redhat
redhatfirefox-0:140.11.0-1.el10_22026-05-27redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(4)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 68× 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.

Showing the most recent 100 of 104 total refreshes for this CVE.

  1. 2026-07-06 16:27 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 02:31 UTCEPSS rescore
  6. 2026-07-05 02:30 UTCEPSS rescore
  7. 2026-07-04 06:31 UTCEPSS rescore
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-01 15:07 UTCEPSS rescore
  10. 2026-06-30 23:22 UTCEPSS rescore
  11. 2026-06-29 14:06 UTCEPSS rescore
  12. 2026-06-28 14:07 UTCEPSS rescore
  13. 2026-06-28 11:38 UTCEG score recompute
  14. 2026-06-28 11:38 UTCVendor advisory
  15. 2026-06-28 11:38 UTCGHSA enrichment
  16. 2026-06-28 04:56 UTCEPSS rescore
  17. 2026-06-27 08:28 UTCEG score recompute
  18. 2026-06-27 08:28 UTCVendor advisory
  19. 2026-06-27 08:28 UTCGHSA enrichment
  20. 2026-06-27 03:08 UTCEPSS rescore
  21. 2026-06-25 23:27 UTCEG score recompute
  22. 2026-06-25 23:27 UTCVendor advisory
  23. 2026-06-25 23:27 UTCGHSA enrichment
  24. 2026-06-25 13:50 UTCEPSS rescore
  25. 2026-06-24 14:05 UTCEPSS rescore
Show 75 more
  1. 2026-06-23 21:33 UTCEPSS rescore
  2. 2026-06-22 14:25 UTCEPSS rescore
  3. 2026-06-21 14:56 UTCEPSS rescore
  4. 2026-06-21 01:59 UTCEPSS rescore
  5. 2026-06-19 19:26 UTCEPSS rescore
  6. 2026-06-18 17:52 UTCEPSS rescore
  7. 2026-06-17 17:53 UTCEPSS rescore
  8. 2026-06-16 17:53 UTCEPSS rescore
  9. 2026-06-16 06:47 UTCEG score recompute
  10. 2026-06-16 06:47 UTCVendor advisory
  11. 2026-06-16 06:47 UTCGHSA enrichment
  12. 2026-06-15 17:49 UTCEPSS rescore
  13. 2026-06-15 17:49 UTCEPSS rescore
  14. 2026-06-14 23:18 UTCEPSS rescore
  15. 2026-06-14 07:44 UTCEG score recompute
  16. 2026-06-14 07:44 UTCVendor advisory
  17. 2026-06-14 07:44 UTCGHSA enrichment
  18. 2026-06-13 23:00 UTCEPSS rescore
  19. 2026-06-13 05:43 UTCEG score recompute
  20. 2026-06-13 05:43 UTCVendor advisory
  21. 2026-06-13 05:43 UTCGHSA enrichment
  22. 2026-06-12 23:12 UTCEPSS rescore
  23. 2026-06-12 23:12 UTCEPSS rescore
  24. 2026-06-12 02:59 UTCEG score recompute
  25. 2026-06-12 02:59 UTCVendor advisory
  26. 2026-06-12 02:59 UTCGHSA enrichment
  27. 2026-06-11 14:00 UTCEPSS rescore
  28. 2026-06-11 00:57 UTCEG score recompute
  29. 2026-06-11 00:57 UTCVendor advisory
  30. 2026-06-11 00:57 UTCGHSA enrichment
  31. 2026-06-10 22:19 UTCEPSS rescore
  32. 2026-06-10 13:22 UTCEPSS rescore
  33. 2026-06-09 22:56 UTCEG score recompute
  34. 2026-06-09 22:56 UTCVendor advisory
  35. 2026-06-09 22:56 UTCGHSA enrichment
  36. 2026-06-08 20:54 UTCEG score recompute
  37. 2026-06-08 20:54 UTCVendor advisory
  38. 2026-06-08 20:54 UTCGHSA enrichment
  39. 2026-06-08 14:17 UTCEPSS rescore
  40. 2026-06-07 18:52 UTCEG score recompute
  41. 2026-06-07 18:52 UTCVendor advisory
  42. 2026-06-07 18:52 UTCGHSA enrichment
  43. 2026-06-07 15:25 UTCEPSS rescore
  44. 2026-06-06 16:49 UTCEG score recompute
  45. 2026-06-06 16:49 UTCVendor advisory
  46. 2026-06-06 16:49 UTCGHSA enrichment
  47. 2026-06-06 13:47 UTCEPSS rescore
  48. 2026-06-05 22:47 UTCEPSS rescore
  49. 2026-06-05 14:47 UTCEG score recompute
  50. 2026-06-05 14:47 UTCVendor advisory
  51. 2026-06-05 14:47 UTCGHSA enrichment
  52. 2026-06-05 06:10 UTCEPSS rescore
  53. 2026-06-04 13:12 UTCEPSS rescore
  54. 2026-06-04 12:44 UTCEG score recompute
  55. 2026-06-04 12:44 UTCVendor advisory
  56. 2026-06-04 12:44 UTCGHSA enrichment
  57. 2026-06-03 10:42 UTCEG score recompute
  58. 2026-06-03 10:42 UTCVendor advisory
  59. 2026-06-03 10:42 UTCGHSA enrichment
  60. 2026-06-02 20:13 UTCEPSS rescore
  61. 2026-06-02 08:40 UTCEG score recompute
  62. 2026-06-02 08:40 UTCVendor advisory
  63. 2026-06-02 08:40 UTCGHSA enrichment
  64. 2026-06-01 13:52 UTCEPSS rescore
  65. 2026-06-01 06:39 UTCEG score recompute
  66. 2026-06-01 06:39 UTCVendor advisory
  67. 2026-06-01 06:39 UTCGHSA enrichment
  68. 2026-05-31 22:30 UTCEPSS rescore
  69. 2026-05-31 00:16 UTCEPSS rescore
  70. 2026-05-29 13:44 UTCEPSS rescore
  71. 2026-05-28 13:44 UTCEPSS rescore
  72. 2026-05-27 13:40 UTCEPSS rescore
  73. 2026-05-27 13:40 UTCEPSS rescore
  74. 2026-05-26 13:44 UTCEPSS rescore
  75. 2026-05-26 07:18 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-8391?
CVE-2026-8391 is a medium vulnerability published on May 12, 2026. Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.
When was CVE-2026-8391 disclosed?
CVE-2026-8391 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8391 actively exploited?
CVE-2026-8391 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-8391?
CVE-2026-8391 has a CVSS v3.1 base score of 5.3 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-8391?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8391, 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-2026-8391

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