CVE-2026-2777 | Privilege escalation in the Messaging System component. This… | CVSS 9.8 CRITICAL

Description

Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Metadata

CVE ID: CVE-2026-2777
State: PUBLISHED
Assigner: mozilla
Reserved: 2026-02-19 15:06 UTC
Published: 2026-02-24 13:33 UTC
Last updated: 2026-07-15 01:13 UTC
Primary CWE: CWE-269
CWE-269 Improper Privilege Management
Vendor / Product: Mozilla / Firefox
Sources: cve.org · NVD

Severity & Metrics

9.8 CRITICAL CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

SSVC — CISA Coordinator

Exploitation: none
Automatable: yes
Tech. Impact: total

Affected products (2)

Vendor	Product	Platform	Versions
Mozilla	Firefox	—	115.33 ≤ 115., 140.8 ≤ 140., 148 ≤ *
Mozilla	Thunderbird	—	140.8 ≤ 140., 148 ≤

Weakness (CWE)

CWE	Source	Description
CWE-269	adp	CWE-269 Improper Privilege Management

CVSS scores (2)

Score	Severity	Version	Source	Vector
9.8	CRITICAL	3.1	adp	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5	HIGH	3.1	adp	CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

References (6)