CVE-2026-3889

MEDIUMNVD 6.56.5
EchelonGraph scoreMEDIUM confidence

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

Score 6.5 from GitHub Security Advisory published 2026-03-24. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
6.5EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100

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)
Severity65% × 45%
Impact severity (EG Severity): CVSS 6.5 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.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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.
EPSS PROB
0.4%
EPSS %ILE
27th
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 (6.5): severity, escalated by confirmed exploitation. This CVE's 6.5 is its impact severity (EG Severity), not escalated.

EG Severity
6.5 MEDIUMCVSS-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 2026-10-17). 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 every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade 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 every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 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 partial (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

March 24, 2026

Last Modified

June 17, 2026

Advisory Details (3)

Auto-updated Aug 4, 2026
Patch available.
Web page

Security Vulnerabilities fixed in Thunderbird 140.9 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-24/
Web page

Security Vulnerabilities fixed in Thunderbird 149 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-23/

Patch Availability(12)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatthunderbird-0:140.9.0-1.el8_42026-04-20redhat
redhatthunderbird-0:140.9.0-1.el9_02026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_62026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_82026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_42026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_62026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_22026-04-15redhat
redhatthunderbird-0:140.9.0-1.el10_02026-04-15redhat
redhatthunderbird-0:140.9.0-1.el9_22026-04-15redhat
redhatthunderbird-0:140.9.0-1.el8_102026-04-07redhat
redhatthunderbird-0:140.9.0-1.el10_12026-04-01redhat
redhatthunderbird-0:140.9.0-1.el9_72026-03-30redhat

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

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
thunderbird1:102.0.1-1 ... 1:91.9.0-1~deb9u1 (306 versions)
  • every version up to 1:140.9.0esr-1~deb11u1: fixed in 1:140.9.0esr-1~deb11u1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
thunderbird1:102.11.0-1 ... 1:140.9.0esr-1~deb11u1 (191 versions)
  • every version up to 1:140.9.0esr-1~deb12u1: fixed in 1:140.9.0esr-1~deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
thunderbird1:128.13.0esr-1 ... 1:140.9.0esr-1~deb11u1 (46 versions)
  • every version up to 1:140.9.0esr-1~deb13u1: fixed in 1:140.9.0esr-1~deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
thunderbird1:128.13.0esr-1 ... 1:140.9.0esr-1~deb13u1 (48 versions)
  • every version up to 1:140.9.0esr-1: fixed in 1:140.9.0esr-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 28× 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 99 of 211 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. 1 repeat row among the latest 100 is merged into the row it repeats. The 112 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  2. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  3. 2026-10-18 03:44 UTCEG score recompute
  4. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  5. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  6. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  7. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  8. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  9. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  10. 2026-10-12 16:10 UTCEG score recompute
  11. 2026-10-11 19:52 UTCEG score recompute
  12. 2026-10-11 17:06 UTCEG score recompute
  13. 2026-10-11 14:32 UTCEG score recompute
  14. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  15. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  16. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  17. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  18. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  19. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.4% · 27th percentile
  20. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  21. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  22. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  23. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  24. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  25. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
Show 74 more
  1. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  2. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  3. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  4. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  5. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  6. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  7. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  8. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  9. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  10. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  11. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  12. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  13. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  14. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  15. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  16. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  17. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  18. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  19. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  20. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  21. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  22. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  23. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  24. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  25. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  26. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  27. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  28. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  29. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  30. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  31. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  32. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  33. 2026-08-16 10:30 UTCEG score recompute
  34. 2026-08-16 10:30 UTCVendor advisory
  35. 2026-08-16 10:30 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  36. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  37. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  38. 2026-08-14 06:48 UTCEG score recompute
  39. 2026-08-14 06:48 UTCVendor advisory
  40. 2026-08-14 06:48 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  41. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  42. 2026-08-12 22:42 UTCEG score recompute
  43. 2026-08-12 22:42 UTCVendor advisory
  44. 2026-08-12 22:42 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  45. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  46. 2026-08-11 21:03 UTCEG score recompute
  47. 2026-08-11 21:03 UTCVendor advisory
  48. 2026-08-11 21:03 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  49. 2026-08-11 13:43 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  50. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  51. 2026-08-10 08:03 UTCEG score recompute
  52. 2026-08-10 08:03 UTCVendor advisory
  53. 2026-08-10 08:03 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  54. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  55. 2026-08-09 06:24 UTCVendor advisory
  56. 2026-08-09 06:24 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  57. 2026-08-07 16:43 UTCEG score recompute
  58. 2026-08-07 16:43 UTCVendor advisory
  59. 2026-08-07 16:43 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  60. 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  61. 2026-08-06 01:09 UTCEG score recompute
  62. 2026-08-06 01:09 UTCVendor advisory
  63. 2026-08-06 01:09 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  64. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  65. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  66. 2026-08-04 10:38 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  67. 2026-08-03 23:54 UTCEG score recompute
  68. 2026-08-03 23:54 UTCVendor advisory
  69. 2026-08-03 23:54 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  70. 2026-08-03 10:36 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  71. 2026-08-02 15:43 UTCEG score recompute
  72. 2026-08-02 15:43 UTCVendor advisory
  73. 2026-08-02 15:43 UTCGHSA enrichmentGHSA-g3qh-qhp8-8f86 · GitHub CVSS 6.5
  74. 2026-08-02 02:27 UTCEPSS rescoreEPSS 0.2% · 10th percentile

Frequently asked(5)

What is CVE-2026-3889?
CVE-2026-3889 is a medium-severity vulnerability; its CVE record was published on March 24, 2026. Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.
When was the CVE record for CVE-2026-3889 published?
The CVE record for CVE-2026-3889 was published on March 24, 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 June 17, 2026; the record at its source may have been updated since.
Is CVE-2026-3889 actively exploited?
CVE-2026-3889 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (27th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-3889?
CVE-2026-3889 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-3889?
A fix for CVE-2026-3889 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-3889 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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