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
22.0%
KEV
Not listed

Published

May 12, 2026

Last Modified

July 15, 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 8× in last 7d / 40× 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. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:25 UTCEPSS rescore
  3. 2026-07-21 15:25 UTCEPSS rescore
  4. 2026-07-20 17:08 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-19 02:29 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-16 17:03 UTCEPSS rescore
  9. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 02:00 UTCEPSS rescore
  11. 2026-07-13 22:31 UTCEPSS rescore
  12. 2026-07-13 06:13 UTCEPSS rescore
  13. 2026-07-12 05:46 UTCEPSS rescore
  14. 2026-07-11 08:27 UTCEPSS rescore
  15. 2026-07-09 19:10 UTCEPSS rescore
  16. 2026-07-07 13:46 UTCEPSS rescore
  17. 2026-07-07 13:46 UTCEPSS rescore
  18. 2026-07-06 16:27 UTCEPSS rescore
  19. 2026-07-06 16:27 UTCEPSS rescore
  20. 2026-07-06 02:23 UTCEPSS rescore
  21. 2026-07-06 02:23 UTCEPSS rescore
  22. 2026-07-05 02:31 UTCEPSS rescore
  23. 2026-07-05 02:30 UTCEPSS rescore
  24. 2026-07-04 06:31 UTCEPSS rescore
  25. 2026-07-04 06:31 UTCEPSS rescore
Show 75 more
  1. 2026-07-01 15:07 UTCEPSS rescore
  2. 2026-06-30 23:22 UTCEPSS rescore
  3. 2026-06-29 14:06 UTCEPSS rescore
  4. 2026-06-28 14:07 UTCEPSS rescore
  5. 2026-06-28 11:38 UTCVendor advisory
  6. 2026-06-28 11:38 UTCGHSA enrichment
  7. 2026-06-28 04:56 UTCEPSS rescore
  8. 2026-06-27 08:28 UTCVendor advisory
  9. 2026-06-27 08:28 UTCGHSA enrichment
  10. 2026-06-27 03:08 UTCEPSS rescore
  11. 2026-06-25 23:27 UTCVendor advisory
  12. 2026-06-25 23:27 UTCGHSA enrichment
  13. 2026-06-25 13:50 UTCEPSS rescore
  14. 2026-06-24 14:05 UTCEPSS rescore
  15. 2026-06-23 21:33 UTCEPSS rescore
  16. 2026-06-22 14:25 UTCEPSS rescore
  17. 2026-06-21 14:56 UTCEPSS rescore
  18. 2026-06-21 01:59 UTCEPSS rescore
  19. 2026-06-19 19:26 UTCEPSS rescore
  20. 2026-06-18 17:52 UTCEPSS rescore
  21. 2026-06-17 17:53 UTCEPSS rescore
  22. 2026-06-16 17:53 UTCEPSS rescore
  23. 2026-06-16 06:47 UTCVendor advisory
  24. 2026-06-16 06:47 UTCGHSA enrichment
  25. 2026-06-15 17:49 UTCEPSS rescore
  26. 2026-06-15 17:49 UTCEPSS rescore
  27. 2026-06-14 23:18 UTCEPSS rescore
  28. 2026-06-14 07:44 UTCVendor advisory
  29. 2026-06-14 07:44 UTCGHSA enrichment
  30. 2026-06-13 23:00 UTCEPSS rescore
  31. 2026-06-13 05:43 UTCVendor advisory
  32. 2026-06-13 05:43 UTCGHSA enrichment
  33. 2026-06-12 23:12 UTCEPSS rescore
  34. 2026-06-12 23:12 UTCEPSS rescore
  35. 2026-06-12 02:59 UTCVendor advisory
  36. 2026-06-12 02:59 UTCGHSA enrichment
  37. 2026-06-11 14:00 UTCEPSS rescore
  38. 2026-06-11 00:57 UTCVendor advisory
  39. 2026-06-11 00:57 UTCGHSA enrichment
  40. 2026-06-10 22:19 UTCEPSS rescore
  41. 2026-06-10 13:22 UTCEPSS rescore
  42. 2026-06-09 22:56 UTCVendor advisory
  43. 2026-06-09 22:56 UTCGHSA enrichment
  44. 2026-06-08 20:54 UTCVendor advisory
  45. 2026-06-08 20:54 UTCGHSA enrichment
  46. 2026-06-08 14:17 UTCEPSS rescore
  47. 2026-06-07 18:52 UTCVendor advisory
  48. 2026-06-07 18:52 UTCGHSA enrichment
  49. 2026-06-07 15:25 UTCEPSS rescore
  50. 2026-06-06 16:49 UTCVendor advisory
  51. 2026-06-06 16:49 UTCGHSA enrichment
  52. 2026-06-06 13:47 UTCEPSS rescore
  53. 2026-06-05 22:47 UTCEPSS rescore
  54. 2026-06-05 14:47 UTCVendor advisory
  55. 2026-06-05 14:47 UTCGHSA enrichment
  56. 2026-06-05 06:10 UTCEPSS rescore
  57. 2026-06-04 13:12 UTCEPSS rescore
  58. 2026-06-04 12:44 UTCVendor advisory
  59. 2026-06-04 12:44 UTCGHSA enrichment
  60. 2026-06-03 10:42 UTCVendor advisory
  61. 2026-06-03 10:42 UTCGHSA enrichment
  62. 2026-06-02 20:13 UTCEPSS rescore
  63. 2026-06-02 08:40 UTCVendor advisory
  64. 2026-06-02 08:40 UTCGHSA enrichment
  65. 2026-06-01 13:52 UTCEPSS rescore
  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 July 15, 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 22.0% 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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