CVE-2020-12405: Race Condition
Last updated 25 August 2025
Other sources
When browsing a malicious page, a race condition in our SharedWorkerService could occur and lead to a potentially exploitable crash.
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
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Firefoxto a version that resolves this vulnerability.Fixed in 77 - Upgrade
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Firefox ESRto a version that resolves this vulnerability.Fixed in 68.9 - Upgrade
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debian/firefoxto a version that resolves this vulnerability.Fixed in 149.0.2-1 - Upgrade
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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/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
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alpine/librewolfto a version that resolves this vulnerability.Fixed in 77.0-r0 - Upgrade
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alpine/mozjs68to a version that resolves this vulnerability.Fixed in 68.9.0-r0 - Upgrade
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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
Event History
Parent advisories
This vulnerability appears in the following advisories.
Peer vulnerabilities
Found alongside the following vulnerabilities.
Frequently Asked Questions
What is CVE-2020-12405?
CVE-2020-12405 is a vulnerability that can occur in Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9 when browsing a malicious page, leading to a potentially exploitable crash due to a race condition in the SharedWorkerService.
How severe is CVE-2020-12405?
CVE-2020-12405 has a severity rating of 5.3 (high).
Which software versions are affected by CVE-2020-12405?
Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9 are affected by CVE-2020-12405.
How can I fix CVE-2020-12405?
To fix CVE-2020-12405, update Thunderbird to 68.9.0 or later, update Firefox to 77.0.1 or later, and update Firefox ESR to 68.9.0 or later.
Where can I find more information about CVE-2020-12405?
You can find more information about CVE-2020-12405 at the following references: [Mozilla Bugzilla](https://bugzilla.mozilla.org/show_bug.cgi?id=1631618), [Mozilla Security Advisory](https://www.mozilla.org/en-US/security/advisories/mfsa2020-22/), [Mozilla Security Advisories](https://www.mozilla.org/security/advisories/mfsa2020-20/).