CVE-2020-26970: Mozilla Thunderbird

High severity, CVSS 8.8. EPSS: 1.2% chance of exploitation in the next 30 days.

When reading SMTP server status codes, Thunderbird writes an integer value to a position on the stack that is intended to contain just one byte. Depending on processor architecture and stack layout, this leads to stack corruption that may be exploitable. This vulnerability affects Thunderbird < 78.5.1.

Affected products

• Mozilla Thunderbird: before 78.5.1 (fixed in 78.5.1)

Published 2020-12-09. Last modified 2026-06-17.