CVE-2026-6771

CRITICALNVD 9.89.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

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, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-24112 (ENISA EUVD) · GHSA-88fc-5m2g-g6q2 (GitHub Security Advisories)Source: ENISA EUVD

9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 9.8Exploit: None knownExposed services: Not assessed

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
9.8CRITICALmedium confidence
EG Risk
59
EG Risk 59/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
23rd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

April 21, 2026

Last Modified

October 26, 2026

Advisory Details (5)

Auto-updated Oct 26, 2026
Patch available.
Web page

Security Vulnerabilities fixed in Thunderbird 140.10 — Mozilla

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

Security Vulnerabilities fixed in Thunderbird 150 — Mozilla

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

Security Vulnerabilities fixed in Firefox ESR 140.10 — Mozilla

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

Security Vulnerabilities fixed in Firefox 150 — Mozilla

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

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

Patch Availability(27)

Vendor / EcosystemFix (by version range) / 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 rangeFix by version rangeDependents
firefox-esr102.1.0esr-1 ... 91.9.1esr-1~deb9u1 (263 versions)
  • every version up to 140.10.0esr-1~deb11u1: fixed in 140.10.0esr-1~deb11u1
—
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (314 versions)
  • every version up to 1:140.10.0esr-1~deb11u1: fixed in 1:140.10.0esr-1~deb11u1
—
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (170 versions)
  • every version up to 140.10.0esr-1~deb12u1: fixed in 140.10.0esr-1~deb12u1
—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (199 versions)
  • every version up to 1:140.10.0esr-1~deb12u1: fixed in 1:140.10.0esr-1~deb12u1
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (46 versions)
  • every version up to 140.10.0esr-1~deb13u1: fixed in 140.10.0esr-1~deb13u1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (55 versions)
  • every version up to 1:140.10.0esr-1~deb13u1: fixed in 1:140.10.0esr-1~deb13u1
—
Debian:14(2)
PackageVulnerable rangeFix by version rangeDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (47 versions)
  • every version up to 140.10.0esr-1: fixed in 140.10.0esr-1
—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (56 versions)
  • every version up to 1:140.10.0esr-1: fixed in 1:140.10.0esr-1
—

Weakness Classification(1)

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

Additional Vendor Advisories

(7)

Data Freshness Timeline

(refreshed 29× in last 7d / 89× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 440 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 340 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-30 04:22 UTCEG score recompute
  2. 2026-10-30 04:22 UTCVendor advisory
  3. 2026-10-30 04:22 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  4. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  5. 2026-10-29 02:26 UTCEG score recompute
  6. 2026-10-29 02:26 UTCVendor advisory
  7. 2026-10-29 02:26 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  8. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  9. 2026-10-28 00:26 UTCEG score recompute
  10. 2026-10-28 00:26 UTCVendor advisory
  11. 2026-10-28 00:26 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  13. 2026-10-26 22:27 UTCEG score recompute
  14. 2026-10-26 22:27 UTCVendor advisory
  15. 2026-10-26 22:27 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  16. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  17. 2026-10-26 12:24 UTCEG score recompute
  18. 2026-10-26 12:24 UTCVendor advisory
  19. 2026-10-26 12:24 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  20. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  21. 2026-10-25 14:10 UTCEG score recompute
  22. 2026-10-25 10:21 UTCEG score recompute
  23. 2026-10-25 10:21 UTCVendor advisory
  24. 2026-10-25 10:21 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
Show 75 more
  1. 2026-10-24 08:24 UTCEG score recompute
  2. 2026-10-24 08:24 UTCVendor advisory
  3. 2026-10-24 08:24 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  4. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  5. 2026-10-23 06:28 UTCEG score recompute
  6. 2026-10-23 06:28 UTCVendor advisory
  7. 2026-10-23 06:28 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  8. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  9. 2026-10-22 04:31 UTCEG score recompute
  10. 2026-10-22 04:31 UTCVendor advisory
  11. 2026-10-22 04:31 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  13. 2026-10-21 02:35 UTCEG score recompute
  14. 2026-10-21 02:35 UTCVendor advisory
  15. 2026-10-21 02:34 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  16. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  17. 2026-10-20 00:37 UTCEG score recompute
  18. 2026-10-20 00:37 UTCVendor advisory
  19. 2026-10-20 00:37 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  20. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  21. 2026-10-18 22:40 UTCEG score recompute
  22. 2026-10-18 22:40 UTCVendor advisory
  23. 2026-10-18 22:39 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  24. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  25. 2026-10-18 03:20 UTCEG score recompute
  26. 2026-10-17 20:42 UTCEG score recompute
  27. 2026-10-17 20:42 UTCVendor advisory
  28. 2026-10-17 20:42 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  29. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  30. 2026-10-16 18:43 UTCEG score recompute
  31. 2026-10-16 18:43 UTCVendor advisory
  32. 2026-10-16 18:43 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  33. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  34. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  35. 2026-10-15 15:43 UTCEG score recompute
  36. 2026-10-15 15:43 UTCVendor advisory
  37. 2026-10-15 15:42 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  38. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  39. 2026-10-14 09:55 UTCEG score recompute
  40. 2026-10-14 09:55 UTCVendor advisory
  41. 2026-10-14 09:55 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  42. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  43. 2026-10-13 07:57 UTCEG score recompute
  44. 2026-10-13 07:57 UTCVendor advisory
  45. 2026-10-13 07:56 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  46. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  47. 2026-10-12 15:45 UTCEG score recompute
  48. 2026-10-12 06:00 UTCVendor advisory
  49. 2026-10-12 05:59 UTCGHSA enrichmentGHSA-88fc-5m2g-g6q2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  50. 2026-10-11 19:30 UTCEG score recompute
  51. 2026-10-11 16:45 UTCEG score recompute
  52. 2026-10-11 14:06 UTCEG score recompute
  53. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  54. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  55. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  56. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  57. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  58. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  59. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  60. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  61. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  62. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  63. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  64. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  65. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  66. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  67. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  68. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  69. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  70. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  71. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  72. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  73. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  74. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
  75. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 23rd percentile

Frequently asked(5)

What is CVE-2026-6771?
CVE-2026-6771 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-6771 published?
The CVE record for CVE-2026-6771 was published on April 21, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-6771 actively exploited?
CVE-2026-6771 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (23rd percentile of EPSS-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?
A fix for CVE-2026-6771 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-6771 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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