What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-20 · updated 2026-10-22
• Weakness: CWE-523

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.

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/

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