6.5

CVE-2025-5271: mozilla firefox Improper Encoding or Escaping of Output

CVSS: 6.5v3.1MediumModified
AliasesUBUNTU-CVE-2025-5271CGA-7573-vr35-vcrpCGA-gph3-cfm8-w76j
Published 27-05-2025Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2025-5271 is a medium (CVSS 6.5) Improper Encoding or Escaping of Output vulnerability in mozilla firefox. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 21.8% of scored vulnerabilities.

Overall risk
26/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.30%
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 2 · Related 4
OPENSUSE-SU-2025:15196-1OPENSUSE-SU-2026:11373-1CGA-285Q-9XQW-XPWPUSN-7991-1

Timeline

  1. 27-05-2025
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

Description

Previewing a response in Devtools ignored CSP headers, which could have allowed content injection attacks. This vulnerability was fixed in Firefox 139 and Thunderbird 139.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.30%

Chance of exploitation in the next 30 days

Percentile

22%

Versus all other CVEs

30-day change

0.00 pp

From 0.30% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.30%

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< 139-r0
  • firefox-esr< 140.5.0-r0 | < 140.4.0-r0
Mozilla1 product
Wolfi1 product
  • firefox< 139-r0

4 vendors · 12 products

References

7 links