9.8

CVE-2026-2777: mozilla firefox Improper Privilege Management

CVSS: 9.8v3.1CriticalModified
AliasesUBUNTU-CVE-2026-2777DEBIAN-CVE-2026-2777CGA-72x5-73fg-5mjv
Published 24-02-2026Last modified 15-07-2026
Open JSON

Vulnerability summary

CVE-2026-2777 is a critical (CVSS 9.8) Improper Privilege Management vulnerability in mozilla firefox. EPSS estimates a 0.58% chance of exploitation in the next 30 days, higher than 46.7% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.58%
0%100%
Low · +0.21 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 39 · Related 9
DLA-4495-1DLA-4496-1DSA-6148-1DSA-6152-1MGASA-2026-0052MGASA-2026-0053

Timeline

  1. 24-02-2026
    PublishedVulnerability first disclosed.
  2. 15-07-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

6 scores · 6 sources · 1 version

EPSS trend

Probability

0.58%

Chance of exploitation in the next 30 days

Percentile

47%

Versus all other CVEs

30-day change

+0.21 pp

From 0.37% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.58%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu8 products
  • mozjs102All versions (No fix recorded)
  • mozjs115All versions (No fix recorded)
  • mozjs38All versions (No fix recorded)
  • mozjs52All versions (No fix recorded)
  • mozjs68All versions (No fix recorded)
Chainguard2 products
  • firefox< 148.0-r0
  • firefox-esr< 140.8.0-r0
Debian2 products
  • firefox-esr< 140.8.0esr-1~deb12u1 | < 140.8.0esr-1~deb13u1 | < 140.8.0esr-1
  • thunderbird< 1:140.8.0esr-1~deb12u1 | < 1:140.8.0esr-1~deb13u1 | < 1:140.8.0esr-1
Mozilla2 products
Wolfi1 product
  • firefox< 148.0-r0

5 vendors · 15 products

References

39 links
Show all 39 references