CVE-2026-3889Network attack vector

User-interface spoofing after user interaction

Published Mar 24, 2026 · Updated Mar 24, 2026

User-interface spoofing in Thunderbird before 149 and before 140.9 allows remote attackers to misrepresent information after user interaction. Mozilla has not disclosed the affected interface locus or the incorrect operation; the referenced bug remains access-restricted. The published assessment requires user interaction and limits the consequence to altered displayed information, without reported data disclosure or service interruption.

CVSS severity6.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

User-interface spoofing in Thunderbird before 149 and before 140.9 allows remote attackers to misrepresent information after user interaction. Mozilla has not disclosed the affected interface locus or the incorrect operation; the referenced bug remains access-restricted. The published assessment requires user interaction and limits the consequence to altered displayed information, without reported data disclosure or service interruption.

The record

CVE
CVE-2026-3889
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
Mozilla
Product
Thunderbird
Classifications
CWE-451
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <140.9
  2. Affected versionversion=unspecified <149

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Thunderbirdversion=unspecified <140.9; version=unspecified <149

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-451User Interface (UI) Misrepresentation of Critical Information

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo