CVE-2025-6427

CRITICALPre-NVD 9.19.1
EchelonGraph scoreMEDIUM confidence

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

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2025-06-26. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: CISA-ADP (Vulnrichment) CVSS v3.1, EPSS, GitHub Security Advisory

Also known asEUVD-2025-21379 (ENISA EUVD) · GHSA-823q-pcrj-c4xv (GitHub Security Advisories)Source: ENISA EUVD

9.1EG
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: 0.4%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

An attacker was able to bypass the connect-src directive of a Content Security Policy by manipulating subdocuments. This would have also hidden the connections from the Network tab in Devtools. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100

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)
Severity91% × 45%
Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 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
0.4%
EPSS %ILE
31st
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 (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.

EG Severity
9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). 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, and whom BOD 26-04 binds: 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.

The score's inputs: 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

June 24, 2025

Last Modified

September 30, 2026

Advisory Details (3)

Auto-updated Sep 16, 2026
Patch available.
Web page

Security Vulnerabilities fixed in Thunderbird 140 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2025-54/
Web page

Security Vulnerabilities fixed in Firefox 140 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2025-51/
Web page

1966927 - (CVE-2025-6427) closed windows and removed iframes can be used to bypass an inherited connect-src CSP and hide network activity from the DevTools

https://bugzilla.mozilla.org/show_bug.cgi?id=1966927

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuxul-ext-lightning (1:140.7.1+build1-0ubuntu0.22.04.1) @ jammy2026-11-11ubuntu

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(1)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 16× in last 7d / 76× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 306 rows 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 206 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-12 22:35 UTCEchelonGraph re-scored
  2. 2026-11-12 22:35 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  3. 2026-11-12 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  4. 2026-11-11 23:49 UTCEchelonGraph re-scored
  5. 2026-11-11 23:49 UTCVendor advisory
  6. 2026-11-11 23:49 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  7. 2026-11-11 16:37 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  8. 2026-11-11 01:30 UTCEchelonGraph re-scored
  9. 2026-11-11 01:30 UTCVendor advisory
  10. 2026-11-11 01:30 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  11. 2026-11-10 16:41 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  12. 2026-11-10 03:10 UTCEchelonGraph re-scored
  13. 2026-11-10 03:10 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  14. 2026-11-09 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  15. 2026-11-09 04:50 UTCEchelonGraph re-scored
  16. 2026-11-09 04:50 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  17. 2026-11-08 16:37 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  18. 2026-11-08 06:31 UTCEchelonGraph re-scored
  19. 2026-11-08 06:31 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  20. 2026-11-07 16:37 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  21. 2026-11-07 08:11 UTCEchelonGraph re-scored
  22. 2026-11-07 08:11 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  23. 2026-11-06 16:35 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  24. 2026-11-06 09:51 UTCEchelonGraph re-scored
  25. 2026-11-06 09:51 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
Show 75 more
  1. 2026-11-05 11:32 UTCEchelonGraph re-scored
  2. 2026-11-05 11:32 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  3. 2026-11-04 16:34 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  4. 2026-11-04 13:12 UTCEchelonGraph re-scored
  5. 2026-11-04 13:12 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  6. 2026-11-03 16:45 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  7. 2026-11-03 14:51 UTCEchelonGraph re-scored
  8. 2026-11-03 14:51 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  9. 2026-11-02 16:43 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  10. 2026-11-02 16:20 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  11. 2026-11-01 17:51 UTCEchelonGraph re-scored
  12. 2026-11-01 17:51 UTCVendor advisory
  13. 2026-11-01 17:51 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  14. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  15. 2026-10-31 19:30 UTCEchelonGraph re-scored
  16. 2026-10-31 19:30 UTCVendor advisory
  17. 2026-10-31 19:30 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  18. 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  19. 2026-10-30 21:11 UTCEchelonGraph re-scored
  20. 2026-10-30 21:11 UTCVendor advisory
  21. 2026-10-30 21:11 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  22. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  23. 2026-10-29 22:51 UTCEchelonGraph re-scored
  24. 2026-10-29 22:51 UTCVendor advisory
  25. 2026-10-29 22:51 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  26. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  27. 2026-10-29 00:32 UTCEchelonGraph re-scored
  28. 2026-10-29 00:32 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  29. 2026-10-28 16:30 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  30. 2026-10-28 02:10 UTCEchelonGraph re-scored
  31. 2026-10-28 02:10 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  32. 2026-10-27 16:30 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  33. 2026-10-27 03:51 UTCEchelonGraph re-scored
  34. 2026-10-27 03:51 UTCVendor advisory
  35. 2026-10-27 03:51 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  36. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  37. 2026-10-26 01:17 UTCEchelonGraph re-scored
  38. 2026-10-26 01:17 UTCVendor advisory
  39. 2026-10-26 01:17 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  40. 2026-10-25 16:31 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  41. 2026-10-25 16:11 UTCEchelonGraph re-scored
  42. 2026-10-25 02:58 UTCEchelonGraph re-scored
  43. 2026-10-25 02:58 UTCVendor advisory
  44. 2026-10-25 02:57 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  45. 2026-10-24 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  46. 2026-10-24 04:38 UTCEchelonGraph re-scored
  47. 2026-10-24 04:38 UTCVendor advisory
  48. 2026-10-24 04:38 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  49. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  50. 2026-10-23 06:17 UTCEchelonGraph re-scored
  51. 2026-10-23 06:17 UTCVendor advisory
  52. 2026-10-23 06:17 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  53. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  54. 2026-10-22 07:55 UTCEchelonGraph re-scored
  55. 2026-10-22 07:55 UTCVendor advisory
  56. 2026-10-22 07:55 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  57. 2026-10-21 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  58. 2026-10-21 09:35 UTCEchelonGraph re-scored
  59. 2026-10-21 09:35 UTCVendor advisory
  60. 2026-10-21 09:35 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  61. 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  62. 2026-10-20 11:14 UTCEchelonGraph re-scored
  63. 2026-10-20 11:14 UTCVendor advisory
  64. 2026-10-20 11:14 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  65. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  66. 2026-10-19 12:54 UTCEchelonGraph re-scored
  67. 2026-10-19 12:54 UTCVendor advisory
  68. 2026-10-19 12:54 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  69. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  70. 2026-10-18 11:37 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  71. 2026-10-18 05:20 UTCEchelonGraph re-scored
  72. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  73. 2026-10-17 13:16 UTCEchelonGraph re-scored
  74. 2026-10-17 13:16 UTCGHSA enrichmentGHSA-823q-pcrj-c4xv · GitHub severity CRITICAL · GitHub CVSS 9.1
  75. 2026-10-16 16:39 UTCEPSS rescoreEPSS 0.4% · 29th percentile

Frequently asked(5)

What is CVE-2025-6427?
CVE-2025-6427 is a critical-severity vulnerability; its CVE record was published on June 24, 2025. An attacker was able to bypass the connect-src directive of a Content Security Policy by manipulating subdocuments. This would have also hidden the connections from the Network tab in Devtools. This vulnerability was fixed in Firefox 140 and Thunderbird 140.
When was the CVE record for CVE-2025-6427 published?
The CVE record for CVE-2025-6427 was published on June 24, 2025. 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 September 30, 2026; the record at its source may have been updated since.
Is CVE-2025-6427 actively exploited?
CVE-2025-6427 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (31st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2025-6427?
CVE-2025-6427 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2025-6427?
A fix for CVE-2025-6427 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

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