CVE-2021-29984
CVSS v3
8.8
HIGH
EPSS Score
1.4 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
Instruction reordering resulted in a sequence of instructions that would cause an object to be incorrectly considered during garbage collection. This led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.
Technical details
- Published
- 2021-08-17
Frequently asked questions
What is CVE-2021-29984?
Instruction reordering resulted in a sequence of instructions that would cause an object to be incorrectly considered during garbage collection. This led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.
Is CVE-2021-29984 actively exploited?
Active exploitation of CVE-2021-29984 has not been confirmed. Its EPSS score was 1.4% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-29984?
CVE-2021-29984 has a CVSS v3 base score of 8.8 (HIGH severity).
Is CVE-2021-29984 affecting your environment?
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