What’s Vulnerable › Vulnerabilities

CVE-2019-9793

• Severity: medium (CVSS 5.9 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-04-26 · updated 2026-06-17
• Weakness: CWE-119

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.

Affected products

• Mozilla Firefox: before 66.0 — fixed in 66.0
• Mozilla Firefox ESR: before 60.6 — fixed in 60.6
• Mozilla Thunderbird: before 60.6 — fixed in 60.6

How to fix

Upgrade to a fixed version: Mozilla Firefox 66.0; Mozilla Firefox ESR 60.6; Mozilla Thunderbird 60.6. Check the vendor advisory for mitigations.

References

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

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