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Fencer Intel
high 8.8

CVE-2020-12409 json

When using certain blank characters in a URL, they where incorrectly rendered as spaces instead of an encoded URL.

published 6y ago modified 4mo ago also EUVD-2020-4721

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits
0
none known

Summary

When using certain blank characters in a URL, they where incorrectly rendered as spaces instead of an encoded URL. This vulnerability affects Firefox < 77.

Patch / fix

  • Mozilla Firefox 77
  • firefox Ubuntu 16.04 LTS 77.0.1+build1-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 77.0.1+build1-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 77.0.1+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-12409

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-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 77.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 77.0-r0

alpine advisories ALPINE-CVE-2020-12409

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 77.0-1

arch linux advisories AVG-1173

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Exploit prediction

1.18% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Firefox

References

Sources

Fencer Intel 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.