CVE-2020-12399: Medium severity Mozilla Thunderbird vulnerability
Last updated 25 August 2025
Other sources
NSS has shown timing differences when performing DSA signatures, which was exploitable and could eventually leak private keys.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 68.9 - Upgrade
Upgrade
Firefoxto a version that resolves this vulnerability.Fixed in 77 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 68.9 - Upgrade
Upgrade
debian/firefoxto a version that resolves this vulnerability.Fixed in 149.0.2-1 - Upgrade
Upgrade
debian/firefox-esrto a version that resolves this vulnerability.Fixed in 115.14.0esr-1~deb11u1Fixed in 140.9.1esr-1~deb11u1Fixed in 128.14.0esr-1~deb12u1Fixed in 140.9.1esr-1~deb12u1Fixed in 140.8.0esr-1~deb13u1Fixed in 140.9.1esr-1~deb13u1Fixed in 140.9.1esr-1 - Upgrade
Upgrade
debian/nssto a version that resolves this vulnerability.Fixed in 2:3.61-1+deb11u3Fixed in 2:3.61-1+deb11u5Fixed in 2:3.87.1-1+deb12u1Fixed in 2:3.87.1-1+deb12u2Fixed in 2:3.110-1+deb13u1Fixed in 2:3.121-1 - Upgrade
Upgrade
debian/thunderbirdto a version that resolves this vulnerability.Fixed in 1:115.12.0-1~deb11u1Fixed in 1:140.9.1esr-1~deb11u1Fixed in 1:140.6.0esr-1~deb12u1Fixed in 1:140.9.1esr-1~deb12u1Fixed in 1:140.8.0esr-1~deb13u1Fixed in 1:140.9.1esr-1~deb13u1Fixed in 1:140.9.0esr-1Fixed in 1:140.9.1esr-1 - Upgrade
Upgrade
alpine/firefoxto a version that resolves this vulnerability.Fixed in 77.0-r0 - Upgrade
Upgrade
alpine/firefox-esrto a version that resolves this vulnerability.Fixed in 68.9.0-r0 - Upgrade
Upgrade
alpine/librewolfto a version that resolves this vulnerability.Fixed in 77.0-r0 - Upgrade
Upgrade
alpine/mozjs68to a version that resolves this vulnerability.Fixed in 68.9.0-r0 - Upgrade
Upgrade
alpine/thunderbirdto a version that resolves this vulnerability.Fixed in 68.9.0-r0 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 68.9.0 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 68.9.0
Event History
Parent advisories
This vulnerability appears in the following advisories.
Peer vulnerabilities
Found alongside the following vulnerabilities.
Frequently Asked Questions
What is the severity of CVE-2020-12399?
The severity of CVE-2020-12399 is high, with a severity value of 4.4.
Which software is affected by CVE-2020-12399?
Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9 are affected by CVE-2020-12399.
What is the impact of CVE-2020-12399?
CVE-2020-12399 could eventually leak private keys due to timing differences in DSA signatures.
How can I fix the vulnerability CVE-2020-12399?
To fix the vulnerability CVE-2020-12399, update Thunderbird to version 68.9.0 or later, update Firefox to version 77 or later, and update Firefox ESR to version 68.9 or later.
Where can I find more information about CVE-2020-12399?
You can find more information about CVE-2020-12399 on the Mozilla bugzilla page (https://bugzilla.mozilla.org/show_bug.cgi?id=1631576), the Mozilla security advisories page (https://www.mozilla.org/en-US/security/advisories/mfsa2020-20/#CVE-2020-12399), and the Mozilla projects page (https://hg.mozilla.org/projects/nss/rev/daa823a4a29bcef0fec33a379ec83857429aea2e).