All vulnerabilities
CVE-2026-113866

Thunderbird: Account password sent unencrypted during Exchange account setup

Mozilla Thunderbird
Open in ThreatlineRecord JSON
CVSS
5.9Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.36%Chance of exploitation activity in the next 30 days, higher than 29% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published20 Oct 2026Updated 20 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Description

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.

Text from CVE List

Affected versions 2

  • Thunderbirdunaffected: 153.5.1 through 153.*CVE List
  • Thunderbirdunaffected: 158.0.1CVE List

References 3