CVE-2021-23978

Firefox ESR and 2 others: Mozilla developers reported memory safety bugs present in Firefox 85 and Firefox ESR 78.7.

CVE-2021-23978 is fixed in 11 products on 2 platforms, first by RHSA-2021:0655, released February 24, 2021. It is not reported as exploited. Patch Radar priority: Urgent.

UrgentFixed on 2 platforms
CVSS
8.8
CRITICAL
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0153
75th percentile

Mozilla developers reported memory safety bugs present in Firefox 85 and Firefox ESR 78.7. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.

Where it's fixed

ProductFixed inFixReleased
Windows apps
Mozilla Firefox ESR (en-US) 91.0 Mozilla Firefox ESR (en-US) 91.0 Aug 4, 2021
Mozilla Thunderbird (en-US) 78.10.0 Mozilla Thunderbird (en-US) 78.10.0 Apr 15, 2021
Linux
firefox · RHEL 8 0:78.8.0-1.el8_3 RHSA-2021:0655 Feb 24, 2021
firefox · Ubuntu 18.04.6 LTS (bionic) 86.0+build3-0ubuntu0.18.04.1 firefox 86.0+build3-0ubuntu0.18.04.1 Feb 26, 2021
firefox · Ubuntu 20.04 LTS (focal) 86.0+build3-0ubuntu0.20.04.1 firefox 86.0+build3-0ubuntu0.20.04.1 Feb 26, 2021
firefox · ol 8 0:78.8.0-1.0.1.el8_3 ELSA-2021-0655 Feb 26, 2021
firefox-geckodriver · Ubuntu 18.04.6 LTS (bionic) 86.0+build3-0ubuntu0.18.04.1 firefox-geckodriver 86.0+build3-0ubuntu0.18.04.1 Feb 26, 2021
firefox-geckodriver · Ubuntu 20.04 LTS (focal) 86.0+build3-0ubuntu0.20.04.1 firefox-geckodriver 86.0+build3-0ubuntu0.20.04.1 Feb 26, 2021
firefox-mozsymbols · Ubuntu 18.04.6 LTS (bionic) 86.0+build3-0ubuntu0.18.04.1 firefox-mozsymbols 86.0+build3-0ubuntu0.18.04.1 Feb 26, 2021
firefox-mozsymbols · Ubuntu 20.04 LTS (focal) 86.0+build3-0ubuntu0.20.04.1 firefox-mozsymbols 86.0+build3-0ubuntu0.20.04.1 Feb 26, 2021
thunderbird · RHEL 8 0:78.8.0-1.el8_3 RHSA-2021:0657 Feb 24, 2021
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) 1:78.8.1+build1-0ubuntu0.20.04.1 thunderbird 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 2021
thunderbird · ol 8 0:78.8.0-1.0.1.el8_3 ELSA-2021-0657 Feb 26, 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) 1:78.8.1+build1-0ubuntu0.20.04.1 thunderbird-gnome-support 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 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) 1:78.8.1+build1-0ubuntu0.20.04.1 thunderbird-mozsymbols 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 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) 1:78.8.1+build1-0ubuntu0.20.04.1 xul-ext-calendar-timezones 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 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) 1:78.8.1+build1-0ubuntu0.20.04.1 xul-ext-gdata-provider 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 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) 1:78.8.1+build1-0ubuntu0.20.04.1 xul-ext-lightning 1:78.8.1+build1-0ubuntu0.20.04.1 Apr 22, 2021

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