CVE-2026-12294

CRITICALPre-NVD 9.69.6—
EchelonGraph scoreMEDIUM confidence

Score 9.6 from GitHub Security Advisory (severity: CRITICAL) published 2026-06-16. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
9.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 9.6Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

CVSS v3
9.6
EG Score
9.6CRITICALmedium confidence
EG Risk
43
EG Risk 43/100

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
Severity96% × 45%
Exploitation0% × 40%
Automatability0% × 15%
EPSS PROB
0.4%
EPSS %ILE
28th
KEV
Not listed

Published

June 16, 2026

Last Modified

July 15, 2026

Advisory Details (10)

Auto-updated Oct 7, 2026
Patch available. Sources: redhat.
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:29940
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 9.

https://access.redhat.com/errata/RHSA-2026:27734
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 10.

https://access.redhat.com/errata/RHSA-2026:27733
redhatMentions a patch (unverified)

Affected: Red Hat Enterprise Linux 8.

https://access.redhat.com/errata/RHSA-2026:27717
generic

Security Vulnerabilities fixed in Thunderbird 140.12 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-61/
generic

Security Vulnerabilities fixed in Thunderbird 152 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-60/
generic

Security Vulnerabilities fixed in Firefox ESR 115.37 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-59/
generic

Security Vulnerabilities fixed in Firefox ESR 140.12 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-58/
generic

Security Vulnerabilities fixed in Firefox 152 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-57/
generic

2039873 - (CVE-2026-12294) PSharedWorker SystemPrincipal escalation via blob:system

https://bugzilla.mozilla.org/show_bug.cgi?id=2039873

Vendor Advisories for CVE-2026-12294(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
redhatthunderbird-0:140.12.0-1.el9_22026-07-15redhat
redhatthunderbird-0:140.12.0-1.el8_82026-07-14redhat
redhatthunderbird-0:140.12.0-1.el8_62026-07-14redhat
redhatthunderbird-0:140.12.0-1.el8_42026-07-14redhat
redhatfirefox-0:140.12.0-1.el7_92026-07-13redhat
redhatthunderbird-0:140.12.0-1.el9_62026-07-13redhat
redhatfirefox-0:140.12.0-1.el9_42026-07-13redhat
redhatthunderbird-0:140.12.0-1.el9_42026-07-13redhat
redhatthunderbird-0:140.12.0-1.el10_02026-07-13redhat
redhatfirefox-0:140.12.0-1.el9_62026-07-09redhat
redhatfirefox-0:140.12.0-1.el8_62026-07-09redhat
redhatfirefox-0:140.12.0-1.el8_42026-07-07redhat
redhatfirefox-0:140.12.0-1.el9_22026-07-07redhat
redhatfirefox-0:140.12.0-1.el8_82026-07-07redhat
redhatfirefox-0:140.12.0-1.el10_02026-07-07redhat
redhatthunderbird-0:140.12.0-1.el8_102026-06-30redhat
redhatthunderbird-0:140.12.0-1.el10_22026-06-29redhat
redhatthunderbird-0:140.12.0-1.el9_82026-06-25redhat
redhatfirefox-0:140.12.0-1.el10_22026-06-22redhat
redhatfirefox-0:140.12.0-1.el8_102026-06-22redhat
redhatfirefox-0:140.12.0-1.el9_82026-06-22redhat

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 (279 versions)
  • every version up to 140.12.0esr-1~deb11u1: fixed in 140.12.0esr-1~deb11u1
—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (330 versions)
  • every version up to 1:140.12.0esr-1~deb11u1: fixed in 1:140.12.0esr-1~deb11u1
—
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (186 versions)
  • every version up to 140.12.0esr-1~deb12u1: fixed in 140.12.0esr-1~deb12u1
—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (215 versions)
  • every version up to 1:140.12.0esr-1~deb12u1: fixed in 1:140.12.0esr-1~deb12u1
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (62 versions)
  • every version up to 140.12.0esr-1~deb13u1: fixed in 140.12.0esr-1~deb13u1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (71 versions)
  • every version up to 1:140.12.0esr-1~deb13u1: fixed in 1:140.12.0esr-1~deb13u1
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (63 versions)
  • every version up to 140.12.0esr-1: fixed in 140.12.0esr-1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (72 versions)
  • every version up to 1:140.12.0esr-1: fixed in 1:140.12.0esr-1
—

Weakness Classification(2)

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 670 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-12294?
CVE-2026-12294 is a critical vulnerability published on June 16, 2026. Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
When was CVE-2026-12294 disclosed?
CVE-2026-12294 was first published on June 16, 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-2026-12294 actively exploited?
CVE-2026-12294 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (28th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-12294?
CVE-2026-12294 has a CVSS v3.1 base score of 9.6 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-12294?
A fix for CVE-2026-12294 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-12294 are linked in the Vendor Advisories panel on this page.

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