9.8

CVE-2026-84637: mozilla thunderbird

CVSS: 9.8v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-84637
Published 01-09-2026Last modified 02-09-2026
Open JSON

Vulnerability summary

CVE-2026-84637 is a critical (CVSS 9.8) vulnerability in mozilla thunderbird. EPSS estimates a 0.63% chance of exploitation in the next 30 days, higher than 49% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.63%
0%100%
Low · +0.29 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 2
MGASA-2026-0388OPENSUSE-SU-2026:12098-1SUSE-SU-2026:4268-1

Timeline

  1. 01-09-2026
    PublishedVulnerability first disclosed.
  2. 02-09-2026
    Last modifiedVulnerability information updated.

Description

Malicious calendar invitations could use file URI attachments to launch local or network-hosted executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new invitation display enabled, the attachment could also appear under a misleading filename. This vulnerability was fixed in Thunderbird 154 and Thunderbird 153.2.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.63%

Chance of exploitation in the next 30 days

Percentile

49%

Versus all other CVEs

30-day change

+0.29 pp

From 0.34% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.63%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Mozilla1 product
Ubuntu1 product
  • thunderbirdAll versions (No fix recorded)

2 vendors · 2 products

References

6 links