What’s Vulnerable › Vulnerabilities

CVE-2019-9815

• Severity: high (CVSS 8.1 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-07-23 · updated 2026-06-17
• Weakness: CWE-203

Description

If hyperthreading is not disabled, a timing attack vulnerability exists, similar to previous Spectre attacks. Apple has shipped macOS 10.14.5 with an option to disable hyperthreading in applications running untrusted code in a thread through a new sysctl. Firefox now makes use of it on the main thread and any worker threads. *Note: users need to update to macOS 10.14.5 in order to take advantage of this change.*. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.

Affected products

• Mozilla Firefox: before 67.0 — fixed in 67.0
• Mozilla Firefox ESR: before 60.7 — fixed in 60.7
• Mozilla Thunderbird: before 60.7 — fixed in 60.7

How to fix

Upgrade to a fixed version: Mozilla Firefox 67.0; Mozilla Firefox ESR 60.7; Mozilla Thunderbird 60.7. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1546544
• https://mdsattacks.com/
• https://www.mozilla.org/security/advisories/mfsa2019-13/
• https://www.mozilla.org/security/advisories/mfsa2019-14/
• https://www.mozilla.org/security/advisories/mfsa2019-15/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1546544
• https://mdsattacks.com/
• https://www.mozilla.org/security/advisories/mfsa2019-13/
• https://www.mozilla.org/security/advisories/mfsa2019-14/
• https://www.mozilla.org/security/advisories/mfsa2019-15/

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