5.1

CVE-2025-0243: mozilla firefox Out-of-bounds Write

CVSS: 5.1v3.1MediumModified
AliasesUBUNTU-CVE-2025-0243DEBIAN-CVE-2025-0243CGA-6fcx-ff3h-qvrg
Published 07-01-2025Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2025-0243 is a medium (CVSS 5.1) Out-of-bounds Write vulnerability in mozilla firefox. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.3% of scored vulnerabilities.

Overall risk
20/100
0100
Low · default modelHow is this calculated?
CVSS score
5.1/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.25%
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 33 · Related 12
DLA-4011-1DLA-4012-1DSA-5839-1DSA-5841-1MGASA-2025-0009MGASA-2025-0010

Timeline

  1. 07-01-2025
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

Description

Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5. 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 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

CVSS metrics

6 scores · 6 sources · 1 version

EPSS trend

Probability

0.25%

Chance of exploitation in the next 30 days

Percentile

15%

Versus all other CVEs

30-day change

0.00 pp

From 0.25% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.25%

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< 134.0+build1-0ubuntu0.20.04.1
  • mozjs102All versions (No fix recorded)
  • mozjs115All versions (No fix recorded)
  • mozjs38All versions (No fix recorded)
  • mozjs52All versions (No fix recorded)
Chainguard2 products
  • firefox< 134.0-r0
  • firefox-esr< 128.6.0-r0
Debian2 products
  • firefox-esr< 128.6.0esr-1~deb12u1 | < 128.6.0esr-1
  • thunderbird< 1:128.6.0esr-1~deb12u1 | < 1:128.6.0esr-1
Mozilla2 products
Wolfi1 product
  • firefox< 134.0-r0

5 vendors · 16 products

References

13 links
Show all 13 references