Medium 5.9Published Oct 20, 2026

CVE-2026-113866Account password sent unencrypted during Exchange account setup

Updated under an hour ago (2026-10-21 19:50 UTC)

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It affects Mozilla Thunderbird. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 5.9 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness (CWE): CWE-523
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: mozilla
NVD analysis: Received
Record last updated: Oct 20, 2026
First seen by InfoSec Signals: Oct 20, 2026

Affected products

Affected products

Mozilla Thunderbird mozilla:thunderbird (from the name)	153.5.1 builds before 153.* not affected; from 158.0.1 not affected	CNA record

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2080121
https://www.mozilla.org/security/advisories/mfsa2026-114/
https://www.mozilla.org/security/advisories/mfsa2026-115/

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.