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Fencer Vulns
medium 6.5

CVE-2020-15654 json

When in an endless loop, a website specifying a custom cursor using CSS could make it look like the user is interacting with the user inter…

published 2020-08-10 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-7641

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

When in an endless loop, a website specifying a custom cursor using CSS could make it look like the user is interacting with the user interface, when they are not. This could lead to a perceived broken state, especially when interactions with existing browser dialogs and warnings do not work. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.

Patch / fix

  • Mozilla Firefox ESR 78.1
  • Mozilla Firefox 79
  • Mozilla Thunderbird 78.1
  • firefox Ubuntu 16.04 LTS 79.0+build1-0ubuntu0.16.04.2
  • firefox Ubuntu 18.04 LTS 79.0+build1-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 79.0+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-2020-15654

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 7 78.3.0-1.el7_9
  • firefox RHEL 8 78.2.0-2.el8_2
  • firefox RHEL 8.0 E4S 78.2.0-3.el8_0
  • firefox RHEL 8.1 EUS 78.2.0-3.el8_1

red hat advisories RHSA-2020:4080RHSA-2020:3555RHSA-2020:3559RHSA-2020:3557

  • MozillaFirefox SLE Module for Desktop Applications 15 SP2 78.1.0-8.3.1
  • pipewire SLE Module for Desktop Applications 15 SP2 0.3.6-3.3.2
  • MozillaFirefox-branding-SLE SLE Module for Desktop Applications 15 SP2 78-9.2.4
  • MozillaFirefox SLE Module for Desktop Applications 15 SP1 78.1.0-3.100.2
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 78.1.0-112.8.1
  • MozillaFirefox SLES 11 SP4-LTSS 78.1.0-78.87.1

suse advisories SUSE-SU-2020:14456-1SUSE-SU-2020:2147-1SUSE-SU-2020:2118-1SUSE-SU-2020:2100-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaFirefox openSUSE Leap 15.2 78.1.0-lp152.2.15.1
  • pipewire openSUSE Leap 15.2 0.3.6-lp152.2.3.1
  • MozillaFirefox openSUSE Leap 15.2 78.1.0-lp152.2.12.1
  • MozillaFirefox openSUSE Leap 15.1 78.1.0-lp151.2.61.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2020:1189-1openSUSE-SU-2020:1155-1openSUSE-SU-2020:1147-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 79.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 79.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.1.0-r0

alpine advisories ALPINE-CVE-2020-15654

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 79.0-1
  • thunderbird Arch Linux 68.12.0-1

arch linux advisories AVG-1213AVG-1214

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-2020-15654 updated cvss 6.5

Mozilla: Custom cursor can overlay user interface

  • Red Hat Enterprise Linux 5 thunderbird Red Hat Enterprise Linux 6 firefox, thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 thunderbird Red Hat Enterprise Linux 8 thunderbird
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 78.2.0-2.el8_2
    fixed: vendor fix RHSA-2020:3557
  • Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox 78.2.0-3.el8_0
    fixed: vendor fix RHSA-2020:3555
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox 78.2.0-3.el8_1
    fixed: vendor fix RHSA-2020:3559
  • Red Hat Enterprise Linux Client (v. 7) firefox 78.3.0-1.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) firefox 78.3.0-1.el7_9 Red Hat Enterprise Linux Server (v. 7) firefox 78.3.0-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) firefox 78.3.0-1.el7_9 Red Hat Enterprise Linux Workstation (v. 7) firefox 78.3.0-1.el7_9 Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 78.3.0-1.el7_9
    fixed: vendor fix RHSA-2020:4080
  • Red Hat Enterprise Linux 5 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

1.42% chance of exploitation in the next 30 days, higher than 73% 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 ESR
  • Mozilla Firefox
  • Mozilla Thunderbird

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

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.