9.8

CVE-2025-1020: mozilla firefox Out-of-bounds Write

CVSS: 9.8v3.1CriticalModified
AliasesUBUNTU-CVE-2025-1020CGA-jvfw-98gr-4xg6CGA-mhm5-r3r3-6h98
Published 04-02-2025Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2025-1020 is a critical (CVSS 9.8) Out-of-bounds Write vulnerability in mozilla firefox. EPSS estimates a 0.54% chance of exploitation in the next 30 days, higher than 44.2% 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
0.54%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 6
OPENSUSE-SU-2025:14730-1OPENSUSE-SU-2026:11373-1USN-7263-1CGA-34R2-37JR-3CPHCGA-7CH3-5PXF-PVGHUSN-7991-1

Timeline

  1. 04-02-2025
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

Description

Memory safety bugs present in Firefox 134 and Thunderbird 134. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 135 and Thunderbird 135.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.54%

Chance of exploitation in the next 30 days

Percentile

44%

Versus all other CVEs

30-day change

0.00 pp

From 0.54% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.54%

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

Ubuntu9 products
  • firefox< 135.0+build2-0ubuntu0.20.04.1
  • mozjs102All versions (No fix recorded)
  • mozjs115All versions (No fix recorded)
  • mozjs38All versions (No fix recorded)
  • mozjs52All versions (No fix recorded)
Chainguard2 products
  • firefox< 135.0-r0
  • firefox-esr< 135-r0
Mozilla2 products
Wolfi1 product
  • firefox< 135.0-r0

4 vendors · 14 products

References

8 links