CVE-2021-29984

HIGHNVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2022-05-24. NVD baseline CVSS 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.8Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
8.8
EG Score
8.8(medium)
EG Risk
—
EPSS
69.4%
KEV
Not listed

Published

August 17, 2021

Last Modified

November 21, 2024

References (14)

Vendor Advisories for CVE-2021-29984(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(10)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntufirefox-mozsymbols (91.0+build2-0ubuntu0.20.04.1) @ focal2026-05-26ubuntu
ubuntuthunderbird-locale-id (1:78.13.0+build1-0ubuntu0.20.04.2) @ focal2026-05-26ubuntu
redhatfirefox-0:78.13.0-2.el7_92021-08-16redhat
redhatthunderbird-0:78.13.0-1.el7_92021-08-16redhat
redhatthunderbird-0:78.13.0-1.el8_42021-08-16redhat
redhatfirefox-0:78.13.0-2.el8_42021-08-16redhat
redhatfirefox-0:78.13.0-2.el8_12021-08-16redhat
redhatthunderbird-0:78.13.0-1.el8_12021-08-16redhat
redhatfirefox-0:78.13.0-2.el8_22021-08-16redhat
redhatthunderbird-0:78.13.0-1.el8_22021-08-16redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(8)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 13× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 22:47 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
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  6. 2026-07-20 17:05 UTCEPSS rescore
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  8. 2026-07-19 02:27 UTCEPSS rescore
  9. 2026-07-19 02:27 UTCEPSS rescore
  10. 2026-07-18 13:59 UTCOSV refresh
  11. 2026-07-18 10:02 UTCEPSS rescore
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  13. 2026-07-16 17:00 UTCEPSS rescore
  14. 2026-07-15 16:55 UTCEPSS rescore
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  22. 2026-07-11 08:25 UTCEPSS rescore
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  24. 2026-07-09 19:07 UTCEPSS rescore
  25. 2026-07-08 15:12 UTCEPSS rescore
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  1. 2026-07-07 13:43 UTCEPSS rescore
  2. 2026-07-06 16:25 UTCEPSS rescore
  3. 2026-07-06 16:25 UTCEPSS rescore
  4. 2026-07-06 02:21 UTCEPSS rescore
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  6. 2026-07-05 02:28 UTCEPSS rescore
  7. 2026-07-04 06:29 UTCEPSS rescore
  8. 2026-07-04 06:29 UTCEPSS rescore
  9. 2026-07-02 16:57 UTCEPSS rescore
  10. 2026-07-01 15:03 UTCEPSS rescore
  11. 2026-06-30 23:20 UTCEPSS rescore
  12. 2026-06-30 23:20 UTCEPSS rescore
  13. 2026-06-30 18:30 UTCOSV refresh
  14. 2026-06-29 14:04 UTCEPSS rescore
  15. 2026-06-28 14:05 UTCEPSS rescore
  16. 2026-06-28 04:54 UTCEPSS rescore
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  18. 2026-06-27 03:06 UTCEPSS rescore
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  20. 2026-06-25 13:48 UTCEPSS rescore
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  22. 2026-06-24 14:03 UTCEPSS rescore
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  24. 2026-06-23 21:31 UTCEPSS rescore
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  26. 2026-06-22 14:24 UTCEPSS rescore
  27. 2026-06-22 14:24 UTCEPSS rescore
  28. 2026-06-21 14:55 UTCEPSS rescore
  29. 2026-06-21 14:54 UTCEPSS rescore
  30. 2026-06-19 19:24 UTCEPSS rescore
  31. 2026-06-19 19:24 UTCEPSS rescore
  32. 2026-06-18 17:51 UTCEPSS rescore
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  34. 2026-06-17 17:51 UTCEPSS rescore
  35. 2026-06-16 17:51 UTCEPSS rescore
  36. 2026-06-15 17:46 UTCEPSS rescore
  37. 2026-06-14 23:15 UTCEPSS rescore
  38. 2026-06-13 22:58 UTCEPSS rescore
  39. 2026-06-13 22:58 UTCEPSS rescore
  40. 2026-06-13 00:08 UTCOSV refresh
  41. 2026-06-12 23:10 UTCEPSS rescore
  42. 2026-06-11 13:58 UTCEPSS rescore
  43. 2026-06-10 22:16 UTCEPSS rescore
  44. 2026-06-10 13:20 UTCEPSS rescore
  45. 2026-06-08 14:15 UTCEPSS rescore
  46. 2026-06-07 15:23 UTCEPSS rescore
  47. 2026-06-07 15:23 UTCEPSS rescore
  48. 2026-06-06 13:46 UTCEPSS rescore
  49. 2026-06-06 13:46 UTCEPSS rescore
  50. 2026-06-06 13:46 UTCEPSS rescore
  51. 2026-06-05 22:45 UTCEPSS rescore
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  55. 2026-06-04 13:10 UTCEPSS rescore
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  60. 2026-06-01 13:50 UTCEPSS rescore
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  62. 2026-05-31 22:29 UTCEPSS rescore
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  64. 2026-05-31 00:15 UTCEPSS rescore
  65. 2026-05-29 13:42 UTCEPSS rescore
  66. 2026-05-28 13:43 UTCEPSS rescore
  67. 2026-05-28 13:43 UTCEPSS rescore
  68. 2026-05-27 13:39 UTCEPSS rescore
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  70. 2026-05-26 13:42 UTCEPSS rescore
  71. 2026-05-26 11:54 UTCEG score recompute
  72. 2026-05-26 11:54 UTCVendor advisory
  73. 2026-05-26 11:54 UTCGHSA enrichment
  74. 2026-05-26 07:17 UTCEPSS rescore
  75. 2026-05-26 07:17 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-29984?
CVE-2021-29984 is a high vulnerability published on August 17, 2021. 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,…
When was CVE-2021-29984 disclosed?
CVE-2021-29984 was first published in the National Vulnerability Database on August 17, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-29984 actively exploited?
CVE-2021-29984 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 69.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-29984?
CVE-2021-29984 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2021-29984?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-29984, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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