Security Resilience

CVE-2026-2782

Mozilla Firefox ≤ 140.8.0

Published
24 February 2026
Modified
13 April 2026
Patch / advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0045 37th percentile
Risk Priority 71 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-2026-2782 is a critical-severity Improper Privilege Management (CWE-269) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).

Operationally, ranked at the 37th 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-2 (Account Management) and AC-24 (Access Control Decisions) — 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-2026-2782 is a privilege escalation vulnerability in the Netmonitor component, affecting Mozilla Firefox and Thunderbird prior to their respective fixed versions. The issue was addressed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. It carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), marking it as critical severity, and is associated with CWE-269 (Improper Privilege Management) alongside NVD-CWE-noinfo.

Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. Successful exploitation enables high-impact outcomes, including unauthorized access to confidential data, modification of system integrity, and denial of service, through privilege escalation within the affected browser or email client components.

Mozilla's security advisories (MFSA2026-13, MFSA2026-15, MFSA2026-16, and MFSA2026-17) and Bugzilla entry 2010743 document the vulnerability and recommend updating to the patched versions—Firefox 148 or ESR 140.8, and Thunderbird 148 or 140.8—for mitigation.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

CWE(s)

Related Threats

CVEs Like This One

CVE-2026-74942Same product: Mozilla Firefox
CVE-2026-6769Same product: Mozilla Firefox
CVE-2026-16401Same product: Mozilla Firefox
CVE-2026-8955Same product: Mozilla Firefox
CVE-2026-92062Same product: Mozilla Firefox
CVE-2026-16371Same product: Mozilla Firefox
CVE-2025-4085Same product: Mozilla Firefox
CVE-2026-8970Same product: Mozilla Firefox
CVE-2026-74985Same product: Mozilla Firefox
CVE-2026-100820Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 140.8.0 · ≤ 148.0
mozilla
thunderbird
≤ 140.8.0 · ≤ 148.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

Account management directly governs assignment and tracking of privileges so proper implementation stops the weakness from being introduced.

Requiring explicit access-control decisions ensures privileges are evaluated rather than assumed or omitted.

Access enforcement applies the correct privilege checks at every request, structurally preventing unintended spheres of control.

Separation of duties constrains how privileges may be assigned, reducing the chance of overly broad actor control.

Least privilege is the direct countermeasure to improper privilege management; implementing it eliminates the root cause.

Binding security attributes to subjects/objects supplies the mechanism needed to track and enforce privileges correctly.

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.

blocks

A.5.15 directly mandates determining access requirements, defining/enforcing topic-specific access control policy, assigning rights/restrictions by entity/role, consistency with classification, need-to-know, privileged access restrictions, segregation, formal authorization, and dynamic rules — which stops most improper privilege management from being exploitable; bounded remainder is flawed implementation of those rules (e.g. incorrect mapping or enforcement bugs).

blocks

A.5.18 directly governs the provisioning, review, modification and timely revocation of access rights (including for role changes, termination and privilege levels), which stops most improper privilege spheres from being exploitable even if the assignment flaw exists; the bounded remainder is flaws in the underlying enforcement mechanism itself (e.g. AC-3/A.8.3)

blocks

Defining and communicating authorization levels for each role limits the assignment of excessive or unnecessary privileges.

A.8.15 Logging partial match
finds

Logging every use of privileges and protecting those records makes it harder for an attacker who has obtained elevated rights to operate without leaving evidence.

blocks

A.8.2 directly controls the identification, allocation, review, expiry, temporary use, and separation of privileged rights per policy, which prevents most improper privilege management (CWE-269) by design; the bounded remainder is flawed tracking/checking logic inside the product's own enforcement code (the AC-3 slice of 269).

blocks

A.8.27 mandates security-by-design principles including least privilege, default deny, fail securely, defence in depth, security architecture integration, hardening, and zero-trust verification of every request; these directly stop most improper privilege spheres from being exploitable even if the assignment flaw remains, with a bounded remainder (e.g. certain legacy or safety-overridden controls).

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

References