# CVE-2019-9815: Information disclosure in Firefox

> Timing attack vulnerability allows attackers to read sensitive data if hyperthreading is enabled, affecting Firefox and Thunderbird users.

- **Severity:** High 8.1 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Jul 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-crxf-6fx4-jr2j, UBUNTU-CVE-2019-9815

## What is CVE-2019-9815?

CVE-2019-9815 is a high-severity vulnerability in Mozilla Firefox, published on 23 Jul 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2019-9815?

It affects 3 products.


Products: Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.

## How do I fix CVE-2019-9815?

Upgrade to a fixed version.

## Is CVE-2019-9815 being exploited?

There is no known exploitation of CVE-2019-9815 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Firefox

- [CVE-2019-11708](https://insights.sbomify.com/CVE-2019-11708/): Mozilla Firefox and Thunderbird Sandbox Escape (critical 10.0, exploited in the wild)
- [CVE-2010-3765](https://insights.sbomify.com/CVE-2010-3765/): Mozilla Multiple Products Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-26486](https://insights.sbomify.com/CVE-2022-26486/): Mozilla Firefox Use-After-Free (critical 9.6, exploited in the wild)
- [CVE-2022-26485](https://insights.sbomify.com/CVE-2022-26485/): Mozilla Firefox Use-After-Free (high 8.8, exploited in the wild)
- [CVE-2019-11707](https://insights.sbomify.com/CVE-2019-11707/): Mozilla Firefox and Thunderbird Type Confusion (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-9815 and fix it if it is affected.

What it is: CVE-2019-9815 is a high-severity vulnerability in Mozilla Firefox, published on 23 Jul 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-9815 in the wild and no public exploit code.

Affected product: Mozilla Firefox. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-9815/ (Markdown: https://insights.sbomify.com/CVE-2019-9815/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-9815
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-9815
- OSV: https://osv.dev/vulnerability/CVE-2019-9815

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-9815/
Summaries are generated and may contain mistakes; the official description above is the record.