# CVE-2019-11736: Firefox ESR: The Mozilla Maintenance Service does not guard against files being hardlinked to another file in the…

CVE-2019-11736 is fixed in Mozilla Firefox ESR (en-US) on 1 platform by Mozilla Firefox ESR (en-US) 78.0esr (version 78.0esr), released June 25, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2019-11736
- Priority: High
- CVSS: 7.0
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 27, 2019
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2019-11736

## Description

The Mozilla Maintenance Service does not guard against files being hardlinked to another file in the updates directory, allowing for the replacement of local files, including the Maintenance Service executable, which is run with privileged access. Additionally, there was a race condition during checks for junctions and symbolic links by the Maintenance Service, allowing for potential local file and directory manipulation to be undetected in some circumstances. This allows for potential privilege escalation by a user with unprivileged local access. <br>*Note: These attacks requires local system access and only affects Windows. Other operating systems are not affected.*. This vulnerability affects Firefox < 69 and Firefox ESR < 68.1.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 78.0esr | [Mozilla Firefox ESR (en-US) 78.0esr](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-78.0esr.md) | Jun 25, 2020 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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