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Fencer Vulns
medium 6.5

CVE-2023-6865 json

`EncryptingOutputStream` was susceptible to exposing uninitialized data.

published 2023-12-19 2 y ago modified 2026-06-17 4 mo ago also EUVD-2023-59069

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits
0
none known

Summary

`EncryptingOutputStream` was susceptible to exposing uninitialized data. This issue could only be abused in order to write data to a local disk which may have implications for private browsing mode. This vulnerability affects Firefox ESR < 115.6 and Firefox < 121.

Patch / fix

  • Mozilla Firefox ESR 115.6
  • Mozilla Firefox 121
  • firefox-esr Debian 12 115.6.0esr-1~deb12u1
  • firefox-esr Debian 14, Debian 13 115.6.0esr-1

debian advisories DEBIAN-CVE-2023-6865

  • firefox Ubuntu 20.04 LTS 121.0+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2023-6865

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 7 115.6.0-1.el7_9
  • firefox RHEL 9 115.6.0-1.el9_3
  • firefox-x11 RHEL 9 115.6.0-1.el9_3
  • firefox RHEL 8 115.6.0-1.el8_9
  • firefox RHEL 9.0 EUS 115.6.0-1.el9_0
  • firefox RHEL 8.2 TUS, RHEL 8.2 E4S, RHEL 8.2 AUS 115.6.0-1.el8_2
  • firefox RHEL 8.4 TUS, RHEL 8.4 E4S, RHEL 8.4 AUS 115.6.0-1.el8_4
  • firefox RHEL 8.6 EUS 115.6.0-1.el8_6

red hat advisories RHSA-2024:0022RHSA-2024:0023RHSA-2024:0021RHSA-2024:0024RHSA-2024:0019RHSA-2024:0026

  • MozillaFirefox SLES for SAP 15 SP4, SLES for SAP 15 SP3, SLES for SAP 15 SP2 +14 more 115.6.0-150200.152.120.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 115.6.0-112.194.1
  • MozillaFirefox SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLE High Performance Computing 15 SP1-LTSS 115.6.0-150000.150.119.1

suse advisories SUSE-SU-2023:4929-1SUSE-SU-2023:4928-1SUSE-SU-2023:4912-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 121.0-1.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:13531-1

  • firefox AlmaLinux 8 115.6.0-1.el8_9.alma
  • firefox AlmaLinux 9 115.6.0-1.el9_3.alma
  • firefox-x11 AlmaLinux 9 115.6.0-1.el9_3.alma

almalinux advisories ALSA-2024:0012ALSA-2024:0025

  • firefox Rocky Linux 8 115.6.0-1.el8_9

rocky linux advisories RLSA-2024:0012

  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +3 more 115.6.0-r0

alpine advisories ALPINE-CVE-2023-6865

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-2023-6865 updated cvss 7.5

Mozilla: Potential exposure of uninitialized data in <code>EncryptingOutputStream</code>

  • Red Hat Enterprise Linux 6 firefox
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 115.6.0-1.el8_9
    fixed: vendor fix RHSA-2024:0012
  • Red Hat Enterprise Linux AppStream (v. 9) firefox 115.6.0-1.el9_3, firefox-x11 115.6.0-1.el9_3
    fixed: vendor fix RHSA-2024:0025
  • Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 115.6.0-1.el8_2
    fixed: vendor fix RHSA-2024:0023
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 115.6.0-1.el8_4
    fixed: vendor fix RHSA-2024:0021
  • Red Hat Enterprise Linux AppStream E4S (v. 8.2) firefox 115.6.0-1.el8_2
    fixed: vendor fix RHSA-2024:0023
  • Red Hat Enterprise Linux AppStream E4S (v.8.4) firefox 115.6.0-1.el8_4
    fixed: vendor fix RHSA-2024:0021
  • Red Hat Enterprise Linux AppStream EUS (v.8.6) firefox 115.6.0-1.el8_6
    fixed: vendor fix RHSA-2024:0024
show 7 more
  • Red Hat Enterprise Linux AppStream EUS (v.8.8) firefox 115.6.0-1.el8_8
    fixed: vendor fix RHSA-2024:0011
  • Red Hat Enterprise Linux AppStream EUS (v.9.0) firefox 115.6.0-1.el9_0
    fixed: vendor fix RHSA-2024:0022
  • Red Hat Enterprise Linux AppStream EUS (v.9.2) firefox 115.6.0-1.el9_2, firefox-x11 115.6.0-1.el9_2
    fixed: vendor fix RHSA-2024:0019
  • Red Hat Enterprise Linux AppStream TUS (v. 8.2) firefox 115.6.0-1.el8_2
    fixed: vendor fix RHSA-2024:0023
  • Red Hat Enterprise Linux AppStream TUS (v.8.4) firefox 115.6.0-1.el8_4
    fixed: vendor fix RHSA-2024:0021
  • Red Hat Enterprise Linux Client (v. 7) firefox 115.6.0-1.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) firefox 115.6.0-1.el7_9 Red Hat Enterprise Linux Server (v. 7) firefox 115.6.0-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) firefox 115.6.0-1.el7_9 Red Hat Enterprise Linux Workstation (v. 7) firefox 115.6.0-1.el7_9 Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 115.6.0-1.el7_9
    fixed: vendor fix RHSA-2024:0026
  • Red Hat Enterprise Linux 6 thunderbird Red Hat Enterprise Linux 7 thunderbird Red Hat Enterprise Linux 8 thunderbird Red Hat Enterprise Linux 9 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

0.89% chance of exploitation in the next 30 days, higher than 59% 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:H/I:N/A:N

Affected products

  • Mozilla Firefox ESR
  • Mozilla Firefox

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.