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CVE Record

CVE-2019-9815: If hyperthreading is not disabled, a timing attack vulnerability exists, similar to previous Spectre attacks.

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2019-9815 concerns a browser and mail-client side-channel risk: under some conditions, timing differences on systems with hyperthreading enabled could leak information, similar to Spectre-class issues. The source names older Mozilla products and notes macOS 10.14.5 support for reducing risk in applications running untrusted code.

Executive priority

Treat this as a legacy software and endpoint hygiene issue unless affected versions remain common in the environment. Prioritize remediation on managed desktops that run untrusted web content or mail attachments, especially older macOS systems.

Technical view

Mozilla describes a timing attack vulnerability when hyperthreading is not disabled. macOS 10.14.5 introduced a sysctl option for applications running untrusted code; Firefox uses it on main and worker threads. Affected products are Thunderbird before 60.7, Firefox before 67, and Firefox ESR before 60.7.

Likely exposure

Exposure is most likely where legacy Firefox, Firefox ESR, or Thunderbird versions remain in use. The macOS-specific mitigation requires macOS 10.14.5. The bundle does not define exposure by processor family, operating system beyond macOS, or deployment configuration.

Exploitation context

The bundle does not show active exploitation, and KEV is false. The issue aligns with speculative-execution timing attacks, which are generally difficult to validate remotely and depend on hardware, threading, and untrusted-code execution context.

Researcher notes

Public details in the bundle are sparse: no CVSS, CWE, proof of exploitation, or processor-specific matrix is provided. Analysis should stay anchored to Mozilla’s affected-version statements and the macOS 10.14.5 hyperthreading-control note.

Mitigation direction

  • Upgrade Firefox to 67 or later where applicable.
  • Upgrade Firefox ESR to 60.7 or later where applicable.
  • Upgrade Thunderbird to 60.7 or later where applicable.
  • On macOS, confirm systems are at least macOS 10.14.5.
  • Check Mozilla and Apple guidance for current side-channel hardening.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across managed endpoints.
  • Identify macOS devices below 10.14.5 that run affected Mozilla software.
  • Confirm browser policy and endpoint controls limit untrusted code exposure.
  • Review vendor advisories for environment-specific mitigation requirements.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2019-9815 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
6Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaThunderbirdunspecifiedListed
MozillaFirefoxunspecifiedListed
MozillaFirefox ESRunspecifiedListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.