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Mozilla CVE-2025-6432

| EUVDEUVD-2025-21376 HIGH
Information Exposure (CWE-200)
2025-06-24 security@mozilla.org
Information Disclosure Mozilla
High
Disputed · 8.6 NVD
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Severity by source

Sources disagree (Low–High)
NVD PRIMARY
8.6 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
Ubuntu
MEDIUM
qualitative
SUSE
HIGH
qualitative
Red Hat
3.4 LOW
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

Lifecycle Timeline

4
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
EUVD ID Assigned
Mar 15, 2026 - 22:36 euvd
EUVD-2025-21376
Analysis Generated
Mar 15, 2026 - 22:36 vuln.today
CVE Published
Jun 24, 2025 - 13:15 nvd
HIGH 8.6

DescriptionCVE.org

When Multi-Account Containers was enabled, DNS requests could have bypassed a SOCKS proxy when the domain name was invalid or the SOCKS proxy was not responding. This vulnerability affects Firefox < 140 and Thunderbird < 140.

AnalysisAI

CVE-2025-6432 is a DNS proxy bypass vulnerability in Firefox and Thunderbird when Mozilla's Multi-Account Containers extension is enabled. Under specific conditions-invalid domain names or unresponsive SOCKS proxies-DNS requests circumvent the configured SOCKS proxy, potentially exposing user browsing activity to network monitoring. This affects Firefox < 140 and Thunderbird < 140, has a high CVSS score of 8.6 reflecting significant confidentiality impact, and requires network-level access but no user interaction to exploit.

Technical ContextAI

The vulnerability resides in the Multi-Account Containers extension's DNS handling when integrated with SOCKS proxy configurations (CWE-200: Information Exposure). When a user configures Firefox/Thunderbird to route traffic through a SOCKS proxy for privacy, the extension should tunnel all DNS queries through that proxy to prevent DNS leaks. However, the implementation contains a logic flaw: if a domain name is malformed/invalid OR the SOCKS proxy is temporarily unreachable, the browser falls back to direct DNS resolution instead of properly queuing or rejecting the request. This creates an information disclosure channel where DNS queries—which reveal visited domains—bypass the proxy's privacy protections. The affected products are Mozilla Firefox (CPE: cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) versions below 140 and Thunderbird (CPE: cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*) versions below 140, specifically in configurations with Multi-Account Containers active and SOCKS proxying enabled.

RemediationAI

  • step: Immediate patching; action: Upgrade Firefox to version 140 or later and Thunderbird to version 140 or later. Updates are available through Mozilla's official channels: https://www.mozilla.org/en-US/firefox/new/ and https://www.thunderbird.net/download/
  • step: Temporary mitigation (pending patch); action: Disable Multi-Account Containers extension in Settings > Extensions & Themes until upgrade is available. Note: This removes container isolation but eliminates the DNS bypass vulnerability.
  • step: Verify proxy configuration; action: Test SOCKS proxy connectivity after patching. Use browser-based DNS leak tests (e.g., dnsleaktest.com) with containers enabled to confirm DNS queries route through proxy. Monitor proxy logs for connection drops that would have triggered the vulnerability.
  • step: Network-level monitoring; action: Implement DNS monitoring/filtering at network perimeter to catch leaked queries. For corporate environments, enforce SOCKS proxy failover to block mode rather than bypass mode.

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Same weakness CWE-200 – Information Exposure

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CVE-2016-6415 HIGH POC
7.5
CVE-2013-7331 MEDIUM POC
6.5
CVE-2025-31125 MEDIUM POC
5.3
CVE-2025-11749 CRITICAL POC
9.8
CVE-2017-16894 HIGH POC
7.5
CVE-2017-11165 CRITICAL POC
9.8
CVE-2016-2388 MEDIUM POC
5.3
CVE-2016-1561 HIGH POC
7.5

Same technique Information Disclosure

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CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5
CVE-2014-6324 HIGH POC
8.8
CVE-2023-7028 CRITICAL POC
10.0
CVE-2017-0213 HIGH POC
7.3

Vendor StatusVendor

Ubuntu

Priority: Medium
firefox
Release Status Version
jammy not-affected code not present
noble not-affected code not present
oracular not-affected code not present
plucky not-affected code not present
upstream needs-triage -
questing not-affected code not present
thunderbird
Release Status Version
noble not-affected code not present
oracular not-affected code not present
plucky not-affected code not present
upstream released 140
jammy released 1:140.7.1+build1-0ubuntu0.22.04.1
questing not-affected code not present
mozjs38
Release Status Version
bionic needs-triage -
jammy DNE -
noble DNE -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs52
Release Status Version
bionic ignored -
focal ignored -
jammy DNE -
noble DNE -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs68
Release Status Version
focal ignored -
jammy DNE -
noble DNE -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs78
Release Status Version
jammy ignored -
noble DNE -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs91
Release Status Version
jammy ignored -
noble DNE -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs102
Release Status Version
jammy ignored -
noble ignored -
oracular DNE -
plucky DNE -
upstream needs-triage -
questing DNE -
mozjs115
Release Status Version
jammy DNE -
noble ignored -
oracular ignored -
plucky ignored -
upstream needs-triage -
questing DNE -
USN-7991-1

Debian

firefox
Release Status Fixed Version Urgency
sid fixed 148.0.2-1 -
(unstable) fixed 140.0-1 -

SUSE

Severity: High
Product Status
Image SLES12-SP5-SAP-Azure-LI-BYOS-Production Image SLES12-SP5-SAP-Azure-VLI-BYOS-Production Affected
Image SLES15-SP4-SAP-Azure-LI-BYOS Image SLES15-SP4-SAP-Azure-LI-BYOS-Production Image SLES15-SP4-SAP-Azure-VLI-BYOS Image SLES15-SP4-SAP-Azure-VLI-BYOS-Production Affected
Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Affected
Image SLES15-SP6-SAP-Azure-LI-BYOS Image SLES15-SP6-SAP-Azure-LI-BYOS-Production Image SLES15-SP6-SAP-Azure-VLI-BYOS Image SLES15-SP6-SAP-Azure-VLI-BYOS-Production Image SLES15-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Enterprise Storage 7.1 Fixed

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CVE-2025-6432 vulnerability details – vuln.today
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