7.5

CVE-2026-84642: mozilla thunderbird

CVSS: 7.5v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-84642
Published 01-09-2026Last modified 02-09-2026
Open JSON

Vulnerability summary

CVE-2026-84642 is a high (CVSS 7.5) vulnerability in mozilla thunderbird. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 34.6% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.42%
0%100%
Low · +0.16 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

The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.42%

Chance of exploitation in the next 30 days

Percentile

35%

Versus all other CVEs

30-day change

+0.16 pp

From 0.25% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.42%

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