CVE-2026-16401

CRITICALPre-NVD 8.89.8
EchelonGraph scoreMEDIUM confidence

“▲” beside the score: it is higher than the CVSS score beside it.

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-21. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 8.8; sources differ by 1.0.

Triggered by: GitHub Security Advisory CVSS
Sources: CISA-ADP (Vulnrichment) CVSS v3.1, EPSS, GitHub Security Advisory
Trending — 3 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 8.8Exploit: None knownExposed services: Not assessed

The CVE record names the fixed release — apply it.

Privilege escalation in the Data Loss Prevention component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

CVSS v3
8.8
EG Score
9.8CRITICALmedium confidence
EG Risk
44
EG Risk 44/100

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 (value × EchelonGraph’s weight)
Severity98% × 45%
The EG Score, 9.8 of 10.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (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: The CVE record names the fixed release. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
10th
KEV
Not listed

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

The CVE record names the fixed release. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (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)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (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

July 21, 2026

Last Modified

July 24, 2026

Advisory Details (3)

Auto-updated Jul 24, 2026
Fix named in the CVE record.
Web page

Security Vulnerabilities fixed in Thunderbird 153 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-71/
Web page

Security Vulnerabilities fixed in Firefox 153 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-68/
Web page

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2052565

Vendor Advisories for CVE-2026-16401(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 16× in last 7d / 59× 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 462 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 362 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 11:42 UTCEG score recompute
  2. 2026-10-14 11:42 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  4. 2026-10-13 10:39 UTCEG score recompute
  5. 2026-10-13 10:38 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  7. 2026-10-12 16:30 UTCEG score recompute
  8. 2026-10-12 09:35 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  9. 2026-10-11 20:09 UTCEG score recompute
  10. 2026-10-11 17:21 UTCEG score recompute
  11. 2026-10-11 14:54 UTCEG score recompute
  12. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  13. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  14. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  15. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  16. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  17. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  18. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  19. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  20. 2026-10-04 14:50 UTCEG score recompute
  21. 2026-10-04 14:50 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  22. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  23. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  24. 2026-10-01 15:05 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-10-01 11:18 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
Show 75 more
  1. 2026-10-01 07:32 UTCEG score recompute
  2. 2026-10-01 07:32 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  4. 2026-09-29 15:20 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  5. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  6. 2026-09-28 09:59 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  7. 2026-09-28 06:11 UTCEG score recompute
  8. 2026-09-28 06:11 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  9. 2026-09-27 13:47 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  10. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  11. 2026-09-24 12:10 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-09-24 08:17 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  13. 2026-09-24 03:24 UTCEG score recompute
  14. 2026-09-24 03:24 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  15. 2026-09-23 09:12 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  16. 2026-09-23 05:24 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  17. 2026-09-23 01:27 UTCEG score recompute
  18. 2026-09-23 01:27 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  19. 2026-09-20 05:59 UTCEG score recompute
  20. 2026-09-20 05:59 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  21. 2026-09-19 00:23 UTCEG score recompute
  22. 2026-09-19 00:23 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  23. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  24. 2026-09-18 11:22 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-09-18 07:36 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  26. 2026-09-18 03:51 UTCEG score recompute
  27. 2026-09-18 03:51 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  28. 2026-09-17 09:53 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  29. 2026-09-17 05:07 UTCEG score recompute
  30. 2026-09-17 05:07 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  31. 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  32. 2026-09-16 12:40 UTCEG score recompute
  33. 2026-09-16 12:40 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  34. 2026-09-16 05:14 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  35. 2026-09-14 10:19 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  36. 2026-09-14 06:11 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  37. 2026-09-14 02:26 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  38. 2026-09-13 22:41 UTCEG score recompute
  39. 2026-09-13 22:41 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  40. 2026-09-13 16:46 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  41. 2026-09-13 15:57 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  42. 2026-09-13 11:26 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  43. 2026-09-13 07:02 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  44. 2026-09-13 03:02 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  45. 2026-09-12 19:11 UTCEG score recompute
  46. 2026-09-12 19:11 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  47. 2026-09-12 15:00 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  48. 2026-09-12 13:33 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  49. 2026-09-12 09:48 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  50. 2026-09-12 05:48 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  51. 2026-09-12 01:54 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  52. 2026-09-11 22:09 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  53. 2026-09-11 18:17 UTCEG score recompute
  54. 2026-09-11 18:17 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  55. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  56. 2026-09-11 09:36 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  57. 2026-09-11 09:08 UTCEG score recompute
  58. 2026-09-11 09:08 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  59. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  60. 2026-09-09 11:34 UTCEG score recompute
  61. 2026-09-09 11:34 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  62. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  63. 2026-09-08 02:26 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  64. 2026-09-07 22:40 UTCEG score recompute
  65. 2026-09-07 22:40 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  66. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  67. 2026-09-06 18:49 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  68. 2026-09-06 14:47 UTCEG score recompute
  69. 2026-09-06 14:47 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  70. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  71. 2026-09-06 11:01 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  72. 2026-09-06 04:04 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  73. 2026-09-05 23:35 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8
  74. 2026-09-05 19:51 UTCEG score recompute
  75. 2026-09-05 19:51 UTCGHSA enrichmentGHSA-96fg-w4m5-jgwc · GitHub severity CRITICAL · GitHub CVSS 9.8

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-16401?
CVE-2026-16401 is a critical-severity vulnerability; its CVE record was published on July 21, 2026. Privilege escalation in the Data Loss Prevention component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
When was the CVE record for CVE-2026-16401 published?
The CVE record for CVE-2026-16401 was published on July 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 July 24, 2026; the record at its source may have been updated since.
Is CVE-2026-16401 actively exploited?
CVE-2026-16401 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (10th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-16401?
CVE-2026-16401 has a CVSS v3.1 base score of 8.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.8 (CRITICAL).
How do I remediate CVE-2026-16401?
The CVE record for CVE-2026-16401 names the fix: "This vulnerability was fixed in Firefox 153 and Thunderbird 153." The vendor advisories EchelonGraph has for CVE-2026-16401 are linked in the Vendor Advisories panel on this page.

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