9.3

CVE-2026-8950: mozilla firefox Origin Validation Error

CVSS: 9.3v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-8950DEBIAN-CVE-2026-8950CGA-66qw-7546-7jvm
Published 19-05-2026Last modified 19-05-2026
Open JSON

Vulnerability summary

CVE-2026-8950 is a critical (CVSS 9.3) Origin Validation Error vulnerability in mozilla firefox. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.3% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.3/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.21%
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 27 · Related 5
MGASA-2026-0164MGASA-2026-0165OPENSUSE-SU-2026:10813-1OPENSUSE-SU-2026:10863-1OPENSUSE-SU-2026:10864-1OPENSUSE-SU-2026:21168-1

Timeline

  1. 19-05-2026
    PublishedVulnerability first disclosed.
  2. 19-05-2026
    Last modifiedVulnerability information updated.

Description

Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.21%

Chance of exploitation in the next 30 days

Percentile

10%

Versus all other CVEs

30-day change

+0.01 pp

From 0.19% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.21%

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< 140.11-r0
  • firefox-esr< 140.11-r0
Debian2 products
  • firefox-esr< 140.11.0esr-1~deb12u1 | < 140.11.0esr-1~deb13u1 | < 140.11.0esr-1
  • thunderbird< 1:140.11.0esr-1~deb12u1 | < 1:140.11.0esr-1~deb13u1 | < 1:140.11.0esr-1
Mozilla2 products
Wolfi1 product
  • firefox< 140.11-r0

5 vendors · 15 products

References

11 links
Show all 11 references