TI-2026-77009 Aliases CVE-2026-113866 GHSA-6c7w-fhrm-qhj3

Thunderbird sends account password unencrypted during Exchange setup

LOW 26CWE-523Published 2026-10-20 · Updated 2026-10-20

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: —
Confidentiality · integrity · availability: High · None · None
Fix status: Partial Red Hat: 3 without a fix

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat.

Summary

During Exchange account setup, Mozilla Thunderbird's AutoDiscover lookup also sends the entered credentials over plain HTTP to the domain's AutoDiscover service. Due to a bug, the credentials are transmitted without encryption (CWE-523). A network attacker who can intercept this traffic can obtain the user's password.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00365 30th percentileScored 2026-11-07

Fix Partial Thunderbird (Mozilla): 153.5.1, 158.0.1Red Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Mozilla	Thunderbird	—	153.5.1, 158.0.1	Patch available	CNA

Thunderbird VendorMozilla Affected — Fixed in 153.5.1, 158.0.1 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:mozilla:thunderbird::::::::	—	—	Mozilla

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions — — ·Mozilla

Remediation

Upgrade Mozilla Thunderbird to 153.5.1 or 158.0.1. The sources list no fixed version for Red Hat Enterprise Linux 8, 9 and 10.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Fix · CNA Thunderbird (Mozilla) Fixed in 153.5.1, 158.0.1

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux 10	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux 8	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux 9	Affected	No fix yet: Fix deferred

Timeline

2026-10-20 Threatist record created from CVE-2026-113866
2026-10-21 Alias added: GHSA-6c7w-fhrm-qhj3
2026-10-21 Affected versions changed · Red Hat
2026-10-21 CVSS score added · Red Hat

References

Other 3

TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8

See all 4204 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences