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Fencer Vulns
medium 6.5

CVE-2020-12415 json

When "%2F" was present in a manifest URL, Firefox's AppCache behavior may have become confused and allowed a manifest to be served from a s…

published 2020-07-09 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4727

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

When "%2F" was present in a manifest URL, Firefox's AppCache behavior may have become confused and allowed a manifest to be served from a subdirectory. This could cause the appcache to be used to service requests for the top level directory. This vulnerability affects Firefox < 78.

Patch / fix

  • Mozilla Firefox 78
  • firefox Ubuntu 16.04 LTS 78.0.1+build1-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 78.0.1+build1-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 78.0.1+build1-0ubuntu0.20.04.1
  • thunderbird Ubuntu 18.04 LTS 1:78.8.1+build1-0ubuntu0.18.04.1
  • thunderbird Ubuntu 20.04 LTS 1:78.7.1+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-12415

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

  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 78.0.1-112.3.1
  • MozillaFirefox-branding-SLE SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +14 more 78-35.3.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP2, SLE Module for Desktop Applications 15 SP1 78.0.1-3.94.2
  • MozillaFirefox-branding-SLE SLE Module for Desktop Applications 15 SP2, SLE Module for Desktop Applications 15 SP1 78-4.14.1
  • MozillaFirefox SLES 11 SP4-LTSS 78.0.1-78.80.2
  • MozillaFirefox-branding-SLED SLES 11 SP4-LTSS 78-21.12.1

suse advisories SUSE-SU-2020:1899-1SUSE-SU-2020:1898-1SUSE-SU-2020:14421-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaFirefox openSUSE Leap 15.1 78.0.1-lp151.2.53.1
  • MozillaFirefox openSUSE Leap 15.2 78.0.1-lp152.2.5.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2020:1017-1openSUSE-SU-2020:0983-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 78.0-r0

alpine advisories ALPINE-CVE-2020-12415

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

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-2020-12415 updated cvss 6.5

Mozilla: AppCache manifest poisoning due to url encoded character processing

  • Red Hat Enterprise Linux 5 thunderbird Red Hat Enterprise Linux 6 thunderbird Red Hat Enterprise Linux 7 thunderbird Red Hat Enterprise Linux 8 thunderbird
    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

1.26% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Firefox

Classification

Weakness
  • CWE-276 Incorrect Default Permissions

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.