Security Resilience

CVE-2026-6765

Mozilla Firefox ≤ 140.10.0

Published
21 April 2026
Modified
22 April 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0036 28th percentile
Risk Priority 44 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-6765 is a medium-severity Exposure of Private Personal Information to an Unauthorized Actor (CWE-359) vulnerability in Mozilla Firefox. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Protocol or Service Impersonation (T1001.003); 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-21 (Information Sharing) and AC-3 (Access Enforcement) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-6765 is an information disclosure vulnerability in the Form Autofill component of Mozilla products. It affects Firefox versions prior to 150, Firefox ESR versions prior to 140.10, Thunderbird versions prior to 150, and Thunderbird versions prior to 140.10. The issue, classified under CWE-359 (Exposure of Private Information to an Unauthorized Actor), carries a CVSS v3.1 base score of 5.3, reflecting medium severity with network accessibility, low attack complexity, no privileges or user interaction required, unchanged scope, and low confidentiality impact.

Unauthenticated remote attackers can exploit this vulnerability over the network without user interaction. Successful exploitation allows disclosure of sensitive information stored or handled by the Form Autofill feature, such as autofill data, though the impact is limited to low confidentiality without affecting integrity or availability.

Mozilla Security Advisories (MFSA 2026-30, 32, 33, and 34) and the associated Bugzilla entry detail the fix applied in the specified versions. Mitigation requires updating to Firefox 150, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10, as no additional workarounds are mentioned.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability Data

Information disclosure in the Form Autofill component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CWE(s)
CWE-359

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001.003 Protocol or Service Impersonation Command And Control
Adversaries may impersonate legitimate protocols or web service traffic to disguise command and control activity and thwart analysis efforts.
attack.mitre.org →
T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1016 System Network Configuration Discovery Discovery
Adversaries may look for details about the network configuration and settings, such as IP and/or MAC addresses, of systems they access or through information discovery of remote systems.
attack.mitre.org →
T1021.002 SMB/Windows Admin Shares Lateral Movement
Adversaries may use [Valid Accounts](https://attack.
attack.mitre.org →
T1021.003 Distributed Component Object Model Lateral Movement
Adversaries may use [Valid Accounts](https://attack.
attack.mitre.org →
T1021.008 Direct Cloud VM Connections Lateral Movement
Adversaries may leverage [Valid Accounts](https://attack.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-1939Same product: Mozilla Firefox
CVE-2025-10859Same product: Mozilla Firefox
CVE-2025-3035Same product: Mozilla Firefox
CVE-2026-8948Same product: Mozilla Firefox
CVE-2026-16353Same product: Mozilla Firefox
CVE-2026-2447Same product: Mozilla Firefox
CVE-2025-1943Same product: Mozilla Firefox
CVE-2026-12310Same product: Mozilla Firefox
CVE-2026-6786Same product: Mozilla Firefox
CVE-2026-6784Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 140.10.0 · ≤ 150.0
mozilla
thunderbird
≤ 140.10.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 2 hardening rules · 2 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V10.3.5
  • V10.7.2

Mitigating Controls (NIST 800-53 r5) AI

AC-3 Access Enforcement good match

Enforces authorizations so that PII is not reachable by unauthorized actors.

AC-21 Information Sharing good match

Requires explicit verification that a recipient's authorizations match the sensitivity of shared PII.

AC-6 Least Privilege good match

Limits granted rights to the minimum needed, reducing the set of actors who can reach private data.

PT-2 Authority to Process Personally Identifiable Information good match

Documents the legal or consent basis required before any processing of PII occurs.

PT-4 Consent good match

Implements consent mechanisms that directly block access absent the individual's permission.

SC-28 Protection of Information at Rest good match

Encrypts or otherwise protects stored PII against unauthorized retrieval.

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.

RC.CO-04 partial match
degrades

CWE-359 does not impair RC.CO-04's ability to issue approved public recovery updates, yet any resulting PII exposure can partially undermine the outcome's overall efficacy and trust.

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.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.5.34 Privacy and protection of PII partial match
blocks

A.5.34 only requires a policy, procedures, roles (e.g. privacy officer) and unspecified 'appropriate' measures; it does not itself stop unauthorized access to PII and depends on other controls (e.g. access enforcement) to do so, per the owner's explicit rule on dependency vs. effect.

A.8.10 Information deletion partial match
removes

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` (higher-evidence rows only; rows rated `none` are excluded).

Ubuntu 22.04 (1 rule)
  • V-260531 Ubuntu 22.04 LTS must configure the SSH daemon to use FIPS 140-3-approved ciphers to prevent the unauthorized disclosure of information and/or detect changes to information during transmission. blocks CWE-359
Ubuntu 24.04 (1 rule)
  • V-270670 Ubuntu 24.04 LTS must configure the SSH client to use FIPS 140-3 approved ciphers to prevent the unauthorized disclosure of information and/or detect changes to information during transmission. blocks CWE-359

References