CVE-2018-18506: Medium severity Mozilla Firefox ESR vulnerability

Published Jan 29, 2019
·
Updated

Last updated 25 August 2025

Other sources

When proxy auto-detection is enabled, if a web server serves a Proxy Auto-Configuration (PAC) file or if a PAC file is loaded locally, this PAC file can specify that requests to the localhost are to be sent through the proxy to another server. This behavior is disallowed by default when a proxy is manually configured, but when enabled could allow for attacks on services and tools that bind to the localhost for networked behavior if they are accessed through browsing.

Affected Software

35 affected componentsFixes available
Mozilla Firefox ESR<60.6
60.6
Mozilla Thunderbird<60.6
60.6
Mozilla Firefox<65
65
Mozilla Firefox<65.0
Canonical Ubuntu Linux=14.04
Canonical Ubuntu Linux=16.04
Canonical Ubuntu Linux=18.04
Canonical Ubuntu Linux=18.10
Debian Debian Linux=8.0
Debian Debian Linux=9.0
redhat Enterprise Linux=8.0
redhat Enterprise Linux Desktop=6.0
redhat Enterprise Linux Desktop=7.0
redhat Enterprise Linux Eus=8.1
redhat Enterprise Linux Eus=8.2
redhat Enterprise Linux Eus=8.4
redhat Enterprise Linux Eus=8.6
redhat Enterprise Linux Server=6.0
redhat Enterprise Linux Server=7.0
redhat Enterprise Linux Server Aus=7.6
redhat Enterprise Linux Server Aus=8.2
redhat Enterprise Linux Server Aus=8.4
redhat Enterprise Linux Server Aus=8.6
redhat Enterprise Linux Server Eus=7.6
redhat Enterprise Linux Server Tus=7.6
redhat Enterprise Linux Server Tus=8.2
redhat Enterprise Linux Server Tus=8.4
redhat Enterprise Linux Server Tus=8.6
redhat Enterprise Linux Workstation=6.0
redhat Enterprise Linux Workstation=7.0
openSUSE Leap=15.0
openSUSE Leap=42.3
debian/firefox
152.0.1-1
debian/firefox-esr
115.14.0esr-1~deb11u1140.12.0esr-1~deb11u1140.10.2esr-1~deb12u1140.12.0esr-1~deb12u1140.10.2esr-1~deb13u1140.12.0esr-1~deb13u1140.11.0esr-1140.12.0esr-1
debian/thunderbird
1:115.12.0-1~deb11u11:140.12.0esr-1~deb11u11:140.10.1esr-1~deb12u11:140.12.0esr-1~deb12u11:140.10.1esr-1~deb13u11:140.12.0esr-1~deb13u11:140.11.0esr-11:140.12.0esr-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 60.6
  2. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 60.6
  3. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 65
  4. Upgrade

    Upgrade debian/firefox to a version that resolves this vulnerability.

    Fixed in 152.0.1-1
  5. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 115.14.0esr-1~deb11u1Fixed in 140.12.0esr-1~deb11u1Fixed in 140.10.2esr-1~deb12u1Fixed in 140.12.0esr-1~deb12u1Fixed in 140.10.2esr-1~deb13u1Fixed in 140.12.0esr-1~deb13u1Fixed in 140.11.0esr-1Fixed in 140.12.0esr-1
  6. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:115.12.0-1~deb11u1Fixed in 1:140.12.0esr-1~deb11u1Fixed in 1:140.10.1esr-1~deb12u1Fixed in 1:140.12.0esr-1~deb12u1Fixed in 1:140.10.1esr-1~deb13u1Fixed in 1:140.12.0esr-1~deb13u1Fixed in 1:140.11.0esr-1Fixed in 1:140.12.0esr-1
  7. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 115.14.0esr-1~deb11u1
  8. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.12.0esr-1~deb11u1
  9. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.10.2esr-1~deb12u1
  10. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.12.0esr-1~deb12u1
  11. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.10.2esr-1~deb13u1
  12. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.12.0esr-1~deb13u1
  13. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.11.0esr-1
  14. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.12.0esr-1
  15. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:115.12.0-1~deb11u1
  16. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.12.0esr-1~deb11u1
  17. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.10.1esr-1~deb12u1
  18. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.12.0esr-1~deb12u1
  19. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.10.1esr-1~deb13u1
  20. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.12.0esr-1~deb13u1
  21. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.11.0esr-1
  22. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.12.0esr-1
  23. Configuration

    Disable proxy auto-detection (WPAD) / 'Auto-detect proxy settings' in the browser Network Settings. Do not load local PAC files that can route localhost requests through a proxy; use manual proxy configuration or no proxy if a proxy is not required.

    Firefox / Thunderbird Proxy auto-detection (WPAD) / Auto-detect proxy settings = disabled

Event History

Jan 29, 2019
CVE Published
via Mozilla·12:00 AM
Feb 5, 2019
CVE Published
via MITRE·09:00 PM
Data Sourced
via MITRE·09:00 PM
DescriptionWeakness
Data Sourced
via NVD·09:29 PM
DescriptionSeverityAffected Software
Mar 20, 2019
Data Sourced
via Red Hat·02:14 AM
DescriptionSeverityAffected Software
Jan 11, 2024
Data Sourced
via Launchpad·10:55 PM
Description
Dec 1, 2025
Data Sourced
via Ubuntu·06:18 PM
RemedyDescriptionSeverityAffected Software
Jun 20, 2026
Data Sourced
via Debian·04:01 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2018-18506?

CVE-2018-18506 has a moderate severity rating, as it affects the handling of Proxy Auto-Configuration (PAC) files.

2

How do I fix CVE-2018-18506?

To fix CVE-2018-18506, update affected software, such as Firefox and Thunderbird, to versions higher than 60.6.

3

What software is affected by CVE-2018-18506?

CVE-2018-18506 affects Mozilla Firefox ESR, Mozilla Thunderbird, and versions of Firefox up to 65.

4

What is the impact of CVE-2018-18506?

CVE-2018-18506 allows a PAC file to route localhost requests through a configured proxy, potentially leading to privacy issues.

5

When was CVE-2018-18506 announced?

CVE-2018-18506 was publicly announced in July 2024.

Company

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