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CVE-2019-9815

21
FAUCET Score

CVE-2019-9815 is a high-severity timing attack vulnerability, akin to Spectre, affecting Mozilla Firefox, Firefox ESR, and Thunderbird on macOS versions prior to 10.14.5. This flaw allows an attacker to potentially extract sensitive information and compromise system integrity and availability if hyperthreading is not disabled. While the CVSS score is 8.1 (High), exploitation requires high attack complexity, and there is no evidence of active exploitation, public exploit code, or significant community discussion. Apple addressed this by providing an option to disable hyperthreading for untrusted code in macOS 10.14.5, which Firefox now utilizes.

Impacted Technologies

VendorProductVersion(s)CPE
< 67.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 60.7CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
< 60.7CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.1HIGH

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.83%
Probability of exploitation in next 30 days
EPSS Percentile
76.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0183 is in the 34th percentile among its peer group of 8,920 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2019-9815Important

Mozilla: Disable hyperthreading on content JavaScript threads on macOS

May 22, 2019

References

bugzilla.mozilla.org / show_bug.cgi
Permissions RequiredThird Party Advisory
mdsattacks.com
Third Party Advisory
mozilla.org / security/advisories/mfsa2019-13
Vendor Advisory
mozilla.org / security/advisories/mfsa2019-14
Vendor Advisory
mozilla.org / security/advisories/mfsa2019-15
Vendor Advisory