CVE-2026-6771

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-21. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0

A fix is available — apply it.

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity98% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
24%
KEV
Not listed

Published

April 21, 2026

Last Modified

April 22, 2026

Advisory Details (5)

Auto-updated Sep 17, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 140.10 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-34/
generic

Security Vulnerabilities fixed in Thunderbird 150 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-33/
generic

Security Vulnerabilities fixed in Firefox ESR 140.10 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-32/
generic

Security Vulnerabilities fixed in Firefox 150 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-30/
generic

2025067 - (CVE-2026-6771) CSP strict-dynamic bypass: XSLT loads exempt from strict-dynamic enforcement, allowing same-origin stylesheet loading when host sources should be ignored

https://bugzilla.mozilla.org/show_bug.cgi?id=2025067

Vendor Advisories for CVE-2026-6771(20)

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

Patch Availability(27)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatthunderbird-0:140.10.0-1.el9_62026-05-20redhat
redhatfirefox-0:140.10.0-1.el9_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_82026-05-20redhat
redhatfirefox-0:140.10.0-2.el7_92026-05-20redhat
redhatfirefox-0:140.10.0-1.el8_62026-05-20redhat
redhatfirefox-0:140.10.0-1.el8_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_22026-05-20redhat
redhatthunderbird-0:140.10.0-1.el9_02026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_62026-05-20redhat
redhatthunderbird-0:140.10.0-1.el8_42026-05-20redhat
redhatthunderbird-0:140.10.0-1.el10_02026-05-20redhat
redhatfirefox-0:140.10.0-1.el10_22026-05-19redhat
redhatthunderbird-0:140.10.0-1.el10_22026-05-19redhat
redhatfirefox-0:140.10.0-1.el9_82026-05-19redhat
redhatthunderbird-0:140.10.1-1.el9_82026-05-19redhat
redhatfirefox-0:140.10.0-1.el10_02026-05-14redhat
redhatfirefox-0:140.10.0-1.el8_82026-05-14redhat
redhatfirefox-0:140.10.0-1.el9_62026-05-14redhat
redhatfirefox-0:140.10.0-1.el9_22026-05-14redhat
redhatfirefox-0:140.10.0-1.el9_02026-05-14redhat
redhatthunderbird-0:140.10.0-1.el9_72026-05-11redhat
redhatthunderbird-0:140.10.0-1.el8_102026-05-04redhat
redhatthunderbird-0:140.10.0-1.el10_12026-04-30redhat
redhatfirefox-0:140.10.0-1.el8_102026-04-27redhat
redhatfirefox-0:140.10.0-1.el9_72026-04-27redhat
redhatfirefox-0:140.10.0-1.el10_12026-04-27redhat

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 rangeFixed inDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (263 versions)140.10.0esr-1~deb11u1—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (314 versions)1:140.10.0esr-1~deb11u1—
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (170 versions)140.10.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (199 versions)1:140.10.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (46 versions)140.10.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (55 versions)1:140.10.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (47 versions)140.10.0esr-1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (56 versions)1:140.10.0esr-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(7)

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 5× in last 7d / 23× 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 346 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-6771?
CVE-2026-6771 is a critical vulnerability published on April 21, 2026. Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
When was CVE-2026-6771 disclosed?
CVE-2026-6771 was first published in the National Vulnerability Database on April 21, 2026, with the most recent update on April 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-6771 actively exploited?
CVE-2026-6771 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 76.1% of all scored CVEs.
What is the CVSS score of CVE-2026-6771?
CVE-2026-6771 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-6771?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-6771, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-6771

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