8.1

CVE-2026-0877: mozilla firefox Protection Mechanism Failure

CVSS: 8.1v3.1HighModified
AliasesUBUNTU-CVE-2026-0877DEBIAN-CVE-2026-0877CGA-cjm2-mm3q-qw4v
Published 13-01-2026Last modified 15-07-2026
Open JSON

Vulnerability summary

CVE-2026-0877 is a high (CVSS 8.1) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39.5% of scored vulnerabilities.

Overall risk
32/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.1/10
010
High · v3.1 (CVE.org)
EPSS score
0.47%
0%100%
Low · -0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 38 · Related 11
DLA-4439-1DLA-4442-1DSA-6101-1DSA-6103-1MGASA-2026-0013MGASA-2026-0014

Timeline

  1. 13-01-2026
    PublishedVulnerability first disclosed.
  2. 15-07-2026
    Last modifiedVulnerability information updated.

Description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS metrics

6 scores · 6 sources · 1 version

EPSS trend

Probability

0.47%

Chance of exploitation in the next 30 days

Percentile

40%

Versus all other CVEs

30-day change

-0.01 pp

From 0.48% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.47%

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< 140.7-r0
  • firefox-esr< 140.7-r0
Debian2 products
  • firefox-esr< 140.7.0esr-1~deb12u1 | < 140.7.0esr-1~deb13u1 | < 140.7.0esr-1
  • thunderbird< 1:140.7.0esr-1~deb12u1 | < 1:140.7.0esr-1~deb13u1 | < 1:140.7.0esr-1
Mozilla2 products
Wolfi1 product
  • firefox< 140.7-r0

5 vendors · 15 products

References

38 links
Show all 38 references