Cyber Resilience

CVE-2025-3932

Auth Bypass in Mozilla Thunderbird ≤ 128.10.1

Auth Bypass
Published
14 May 2025
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
EPSS Score 0.0035 28th percentile
Risk Priority 50 floored blend · peak EPSS

Summary

CVE-2025-3932 is a medium-severity Authentication Bypass Using an Alternate Path or Channel (CWE-288) vulnerability in Mozilla Thunderbird. Its CVSS base score is 6.5 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 28th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has…

more

been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

CWE(s)
CWE-288

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1542.002 Component Firmware Stealth
Adversaries may modify component firmware to persist on systems.
attack.mitre.org →
T1556 Modify Authentication Process Defense Impairment
Adversaries may modify authentication mechanisms and processes to access user credentials or enable otherwise unwarranted access to accounts.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-2775Same product: Mozilla Thunderbird
CVE-2026-6768Same product: Mozilla Thunderbird
CVE-2026-2791Same product: Mozilla Thunderbird
CVE-2025-10531Same product: Mozilla Thunderbird
CVE-2026-6760Same product: Mozilla Thunderbird
CVE-2026-6771Same product: Mozilla Thunderbird
CVE-2026-2784Same product: Mozilla Thunderbird
CVE-2025-2830Same product: Mozilla Thunderbird
CVE-2025-0510Same product: Mozilla Thunderbird
CVE-2026-57963Same product: Mozilla Thunderbird

Affected Assets

mozilla
thunderbird
≤ 128.10.1 · 129.0 — 138.0.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 7 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V6.4.3
  • V6.6.1
  • V12.1.3

Mitigating Controls (NIST 800-53 r5) AI

AC-25 Reference Monitor good match

Requires a tamperproof, always-invoked reference monitor that structurally blocks bypass via any alternate path.

AC-3 Access Enforcement good match

Enforces authorization checks on every logical access path, eliminating unauthenticated alternate channels.

IA-2 Identification and Authentication (Organizational Users) good match

Mandates unique identification and authentication for all organizational users, covering the primary authentication requirement.

SC-7 Boundary Protection partial match

Controls all external and key internal interfaces, reducing the chance of unauthenticated alternate channels.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-03 full match
prevents

Requiring authentication on every channel and path directly eliminates alternate-path bypasses.

PR.AA-05 mostly match
prevents

Enforcing authorizations and least privilege across all access vectors prevents unauthenticated alternate paths.

PR.IR-01 mostly match
prevents

Protecting networks and environments from unauthorized logical access blocks bypass via undocumented channels.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect alternate-path bypasses but does not prevent them in production.

A.8.5 Secure authentication mostly match
degrades

Secure authentication control directly mitigates bypass by requiring strong, consistent authentication on all paths.

A.5.15 Access control partial match
prevents

Access control policy directly addresses alternate authentication paths by requiring all channels to enforce authentication.

A.5.17 Authentication information partial match
degrades

Authentication information management ensures credentials and mechanisms are consistently applied across all access paths.

A.5.18 Access rights partial match
prevents

Access rights provisioning and review prevent bypass via unmonitored or alternate channels.

A.8.2 Privileged access rights partial match
prevents

Privileged access rights control reduces risk of bypass through elevated or alternate paths.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (2 rules)
  • V-248598 There must be no ".shosts" files on the OL 8 operating system. prevents CWE-288
  • V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-288
Oracle Linux 9 (2 rules)
  • V-271757 OL 9 file systems must not contain shosts.equiv files. prevents CWE-288
  • V-271758 OL 9 file systems must not contain .shosts files. prevents CWE-288
RHEL 7 (3 rules)
  • V-204440 Red Hat Enterprise Linux operating systems version 7.2 or newer using Unified Extensible Firmware Interface (UEFI) must require authentication upon booting into single-user and maintenance modes. prevents CWE-288
  • V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-288
  • V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. prevents CWE-288

References