Skip to content
Fencer Vulns
critical 9.8

CVE-2020-12390 json

Incorrect origin serialization of URLs with IPv6 addresses could lead to incorrect security checks.

published 2020-05-26 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4702

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.6%
EPSS 1.6% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

Incorrect origin serialization of URLs with IPv6 addresses could lead to incorrect security checks. This vulnerability affects Firefox < 76.

Patch / fix

  • Mozilla Firefox 76
  • firefox Ubuntu 16.04 LTS 76.0+build2-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 76.0+build2-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 76.0+build2-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-12390

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox RHEL 8 78.2.0-2.el8_2

red hat advisories RHSA-2020:3557

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 76.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 76.0-r0

alpine advisories ALPINE-CVE-2020-12390

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox Arch Linux 76.0-1

arch linux advisories AVG-1148

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12390 updated cvss 9.8

Mozilla: Incorrect serialization of nsIPrincipal.origin for IPv6 addresses

  • Red Hat Enterprise Linux 5 firefox Red Hat Enterprise Linux 6 firefox
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 78.2.0-2.el8_2
    fixed: vendor fix RHSA-2020:3557
  • Red Hat Enterprise Linux 7 firefox
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.62% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Firefox

Classification

Weakness
  • CWE-502 Deserialization of Untrusted Data

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.