# CVE-2020-15657: Firefox ESR and 2 others: Firefox could be made to load attacker-supplied DLL files from the installation directory.

CVE-2020-15657 is fixed in 2 products on 1 platform, first by Mozilla Thunderbird (en-US) 78.1.0, released July 29, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2020-15657
- Priority: High
- CVSS: 7.8
- EPSS: 0.0035
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 10, 2020
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2020-15657

## Description

Firefox could be made to load attacker-supplied DLL files from the installation directory. This required an attacker that is already capable of placing files in the installation directory. *Note: This issue only affected Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 91.0 | [Mozilla Firefox ESR (en-US) 91.0](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-91.0.md) | Aug 4, 2021 |
| Windows apps | Mozilla Thunderbird (en-US) | 78.1.0 | [Mozilla Thunderbird (en-US) 78.1.0](https://patchblox.com/security/data/fix/windows-app/mozilla.thunderbird-78.1.0.md) | Jul 29, 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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