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Fencer Vulns
medium 6.5

CVE-2023-5171 json

During Ion compilation, a Garbage Collection could have resulted in a use-after-free condition, allowing an attacker to write two NUL bytes…

published 2023-09-27 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-57508

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 66%
public exploits
0
none known

Summary

During Ion compilation, a Garbage Collection could have resulted in a use-after-free condition, allowing an attacker to write two NUL bytes, and cause a potentially exploitable crash. This vulnerability affects Firefox < 118, Firefox ESR < 115.3, and Thunderbird < 115.3.

Patch / fix

  • Mozilla Firefox 118
  • Mozilla Firefox ESR 115.3
  • Mozilla Thunderbird 115.3
  • firefox-esr Debian 12 115.3.0esr-1~deb12u1
  • firefox-esr Debian 14, Debian 13 115.3.0esr-1
  • thunderbird Debian 12 1:115.3.1-1~deb12u1
  • thunderbird Debian 14, Debian 13 1:115.3.0-1

debian advisories DEBIAN-CVE-2023-5171

  • firefox Ubuntu 20.04 LTS 118.0.1+build1-0ubuntu0.20.04.1
  • thunderbird Ubuntu 20.04 LTS 1:115.3.1+build1-0ubuntu0.20.04.1
  • thunderbird Ubuntu 22.04 LTS 1:115.3.1+build1-0ubuntu0.22.04.2

ubuntu advisories UBUNTU-CVE-2023-5171

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 8 115.3.1-1.el8_8
  • thunderbird RHEL 8 115.3.1-1.el8_8
  • thunderbird RHEL 7 115.3.1-1.el7_9
  • firefox RHEL 7 115.3.1-1.el7_9
  • thunderbird RHEL 9 115.3.1-1.el9_2
  • firefox RHEL 9 115.3.1-1.el9_2
  • firefox-x11 RHEL 9 115.3.1-1.el9_2
  • thunderbird RHEL 8.2 TUS, RHEL 8.2 E4S, RHEL 8.2 AUS 115.3.1-1.el8_2

red hat advisories RHSA-2023:5432RHSA-2023:5436RHSA-2023:5433RHSA-2023:5428RHSA-2023:5475RHSA-2023:5430

  • MozillaThunderbird SLE Workstation Extension 15 SP5, SLE Workstation Extension 15 SP4, SLE Module for Package Hub 15 SP5 +3 more 115.3.1-150200.8.133.1
  • MozillaFirefox SLES for SAP 15 SP3, SLES for SAP 15 SP2, SLES 15 SP3-LTSS +9 more 115.3.0-150200.152.108.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 115.3.0-112.182.1
  • MozillaFirefox SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLE High Performance Computing 15 SP1-LTSS 115.3.0-150000.150.107.1

suse advisories SUSE-SU-2023:4016-1SUSE-SU-2023:3899-1SUSE-SU-2023:3898-1SUSE-SU-2023:3837-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaThunderbird openSUSE Tumbleweed 115.3.0-1.1
  • MozillaFirefox openSUSE Tumbleweed 118.0.1-1.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:13268-1openSUSE-SU-2024:13272-1

  • firefox AlmaLinux 9 115.3.1-1.el9_2.alma.1
  • firefox-x11 AlmaLinux 9 115.3.1-1.el9_2.alma.1
  • thunderbird AlmaLinux 9 115.3.1-1.el9_2.alma

almalinux advisories ALSA-2023:5434ALSA-2023:5435

  • thunderbird Rocky Linux 9 115.3.1-1.el9_2
  • thunderbird Rocky Linux 8 115.3.1-1.el8_8

rocky linux advisories RLSA-2023:5435RLSA-2023:5428

  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +3 more 115.3.0-r0

alpine advisories ALPINE-CVE-2023-5171

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-2023-5171 updated cvss 6.5

Mozilla: Use-after-free in Ion Compiler

  • Red Hat Enterprise Linux 6 firefox, thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 115.3.1-1.el8_8, thunderbird 115.3.1-1.el8_8
    fixed: vendor fix RHSA-2023:5433
  • Red Hat Enterprise Linux AppStream (v. 9) firefox 115.3.1-1.el9_2, firefox-x11 115.3.1-1.el9_2, thunderbird 115.3.1-1.el9_2
    fixed: vendor fix RHSA-2023:5434
  • Red Hat Enterprise Linux AppStream AUS (v. 8.2) firefox 115.3.1-1.el8_2, thunderbird 115.3.1-1.el8_2
    fixed: vendor fix RHSA-2023:5426
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 115.3.1-1.el8_4, thunderbird 115.3.1-1.el8_4
    fixed: vendor fix RHSA-2023:5437
  • Red Hat Enterprise Linux AppStream E4S (v. 8.1) firefox 115.3.1-1.el8_1, thunderbird 115.3.1-1.el8_1
    fixed: vendor fix RHSA-2023:5440
  • Red Hat Enterprise Linux AppStream E4S (v. 8.2) firefox 115.3.1-1.el8_2, thunderbird 115.3.1-1.el8_2
    fixed: vendor fix RHSA-2023:5426
  • Red Hat Enterprise Linux AppStream E4S (v.8.4) firefox 115.3.1-1.el8_4, thunderbird 115.3.1-1.el8_4
    fixed: vendor fix RHSA-2023:5437
show 5 more
  • Red Hat Enterprise Linux AppStream EUS (v.8.6) firefox 115.3.1-1.el8_6, thunderbird 115.3.1-1.el8_6
    fixed: vendor fix RHSA-2023:5436
  • Red Hat Enterprise Linux AppStream EUS (v.9.0) firefox 115.3.1-1.el9_0, thunderbird 115.3.1-1.el9_0
    fixed: vendor fix RHSA-2023:5427
  • Red Hat Enterprise Linux AppStream TUS (v. 8.2) firefox 115.3.1-1.el8_2, thunderbird 115.3.1-1.el8_2
    fixed: vendor fix RHSA-2023:5426
  • Red Hat Enterprise Linux AppStream TUS (v.8.4) firefox 115.3.1-1.el8_4, thunderbird 115.3.1-1.el8_4
    fixed: vendor fix RHSA-2023:5437
  • Red Hat Enterprise Linux Client (v. 7) firefox 115.3.1-1.el7_9, thunderbird 115.3.1-1.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) firefox 115.3.1-1.el7_9 Red Hat Enterprise Linux Server (v. 7) firefox 115.3.1-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) firefox 115.3.1-1.el7_9, thunderbird 115.3.1-1.el7_9 Red Hat Enterprise Linux Workstation (v. 7) firefox 115.3.1-1.el7_9, thunderbird 115.3.1-1.el7_9 Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 115.3.1-1.el7_9
    fixed: vendor fix RHSA-2023:5477

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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.12% chance of exploitation in the next 30 days, higher than 66% 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:N/A:H

Affected products

  • Mozilla Firefox
  • Mozilla Firefox ESR
  • Mozilla Thunderbird

Classification

Weakness

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.