CVE-2026-8391

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2026-05-12. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 5.3Exploit: None knownExposed services: Not assessed

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
5.3MEDIUMmedium confidence
EG Risk
39
EG Risk 39/100

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
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
EPSS PROB
0.6%
EPSS %ILE
44th
KEV
Not listed

Published

May 12, 2026

Last Modified

July 15, 2026

Advisory Details (5)

Auto-updated Jun 16, 2026
Patch available.
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 / EcosystemFix (by version range) / 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.

Affected Packages

(8 across 4 ecosystems)
Debian:11(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (275 versions)
  • every version up to 140.11.0esr-1~deb11u1: fixed in 140.11.0esr-1~deb11u1
—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (326 versions)
  • every version up to 1:140.11.0esr-1~deb11u1: fixed in 1:140.11.0esr-1~deb11u1
—
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (182 versions)
  • every version up to 140.11.0esr-1~deb12u1: fixed in 140.11.0esr-1~deb12u1
—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (211 versions)
  • every version up to 1:140.11.0esr-1~deb12u1: fixed in 1:140.11.0esr-1~deb12u1
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (58 versions)
  • every version up to 140.11.0esr-1~deb13u1: fixed in 140.11.0esr-1~deb13u1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (67 versions)
  • every version up to 1:140.11.0esr-1~deb13u1: fixed in 1:140.11.0esr-1~deb13u1
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (59 versions)
  • every version up to 140.11.0esr-1: fixed in 140.11.0esr-1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (68 versions)
  • every version up to 1:140.11.0esr-1: fixed in 1:140.11.0esr-1
—

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 6× in last 7d / 25× 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 219 total refreshes for this CVE.

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

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 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 0.6% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
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?
A fix for CVE-2026-8391 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-8391 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-8391

Explore →

Is Your Infrastructure Affected by CVE-2026-8391?

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

Book a Demo →Browse All CVEs