Firefox ESR and 2 others: JIT optimizations involving the Javascript arguments object could confuse later optimizations.
CVE-2020-15656 is fixed in 11 products on 2 platforms, first by Mozilla Thunderbird (en-US) 78.1.0, released July 29, 2020. It is not reported as exploited. Patch Radar priority: High.
JIT optimizations involving the Javascript arguments object could confuse later optimizations. This risk was already mitigated by various precautions in the code, resulting in this bug rated at only moderate severity. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Mozilla Firefox ESR (en-US) | 91.0 | Mozilla Firefox ESR (en-US) 91.0 | Aug 4, 2021 |
| Mozilla Thunderbird (en-US) | 78.1.0 | Mozilla Thunderbird (en-US) 78.1.0 | Jul 29, 2020 |
| Linux | |||
| firefox · RHEL 8 | 0:78.2.0-2.el8_2 | RHSA-2020:3557 | Aug 26, 2020 |
| firefox · Ubuntu 18.04.6 LTS (bionic) | 79.0+build1-0ubuntu0.18.04.1 | firefox 79.0+build1-0ubuntu0.18.04.1 | Aug 10, 2020 |
| firefox · Ubuntu 20.04 LTS (focal) | 79.0+build1-0ubuntu0.20.04.1 | firefox 79.0+build1-0ubuntu0.20.04.1 | Aug 10, 2020 |
| firefox · ol 8 | 0:78.2.0-2.0.1.el8_2 | ELSA-2020-3557 | Aug 28, 2020 |
| firefox-geckodriver · Ubuntu 18.04.6 LTS (bionic) | 79.0+build1-0ubuntu0.18.04.1 | firefox-geckodriver 79.0+build1-0ubuntu0.18.04.1 | Aug 10, 2020 |
| firefox-geckodriver · Ubuntu 20.04 LTS (focal) | 79.0+build1-0ubuntu0.20.04.1 | firefox-geckodriver 79.0+build1-0ubuntu0.20.04.1 | Aug 10, 2020 |
| firefox-mozsymbols · Ubuntu 18.04.6 LTS (bionic) | 79.0+build1-0ubuntu0.18.04.1 | firefox-mozsymbols 79.0+build1-0ubuntu0.18.04.1 | Aug 10, 2020 |
| firefox-mozsymbols · Ubuntu 20.04 LTS (focal) | 79.0+build1-0ubuntu0.20.04.1 | firefox-mozsymbols 79.0+build1-0ubuntu0.20.04.1 | Aug 10, 2020 |
| thunderbird · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | thunderbird 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| thunderbird · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | thunderbird 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
| thunderbird-gnome-support · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | thunderbird-gnome-support 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| thunderbird-gnome-support · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | thunderbird-gnome-support 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
| thunderbird-mozsymbols · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | thunderbird-mozsymbols 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| thunderbird-mozsymbols · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | thunderbird-mozsymbols 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
| xul-ext-calendar-timezones · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | xul-ext-calendar-timezones 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| xul-ext-calendar-timezones · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | xul-ext-calendar-timezones 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
| xul-ext-gdata-provider · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | xul-ext-gdata-provider 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| xul-ext-gdata-provider · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | xul-ext-gdata-provider 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
| xul-ext-lightning · Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | xul-ext-lightning 1:78.8.1+build1-0ubuntu0.18.04.1 | Apr 22, 2021 |
| xul-ext-lightning · Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | xul-ext-lightning 1:78.7.1+build1-0ubuntu0.20.04.1 | Jan 25, 2021 |
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