CVE-2023-5171

20

FAUCET Score

CVE-2023-5171 is a use-after-free vulnerability in Mozilla Firefox, Firefox ESR, and Thunderbird, occurring during Ion compilation due to a Garbage Collection error. This flaw allows an attacker to write two NUL bytes, potentially leading to an exploitable crash. Rated as Medium severity (CVSS 6.5), it requires user interaction and could result in a denial of service. There is no evidence of active exploitation, public exploit code, or inclusion in CISA's KEV catalog, though it has received limited community discussion and media coverage.

Impacted Technologies

Vendor	Product	Version(s)	CPE
		< 118CPE matchmatch criteria	cpe:2.3:a:mozilla:firefox::::::::
		< 115.3CPE matchmatch criteria	cpe:2.3:a:mozilla:firefox_esr::::::::
		< 115.3CPE matchmatch criteria	cpe:2.3:a:mozilla:thunderbird::::::::
		10.0CPE matchmatch criteria	cpe:2.3:o:debian:debian_linux:10.0:::::::*
		11.0CPE matchmatch criteria	cpe:2.3:o:debian:debian_linux:11.0:::::::*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

Exploitability Score

2.8

Impact Score

3.6

CvssVersion

3.1

Exploit Intelligence

EPSS Score

1.02%

Probability of exploitation in next 30 days

EPSS Percentile

59.9%

Percentile rank of EPSS score among Peer Group

As of 2026-07-28

Model: v2026.06.15

This CVE's current EPSS score of 0.0102 is in the 72nd percentile among its peer group of 26,236 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (26)

debianpatch availablevia nvd_reference

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:115.3.1-1.el7_9

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:115.3.1-1.el7_9

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:115.3.1-1.el8_8

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:115.3.1-1.el8_8

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.1 Update Services for SAP SolutionsFixed in: thunderbird-0:115.3.1-1.el8_1

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.1 Update Services for SAP SolutionsFixed in: firefox-0:115.3.1-1.el8_1

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: firefox-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: thunderbird-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Telecommunications Update ServiceFixed in: firefox-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Telecommunications Update ServiceFixed in: thunderbird-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Update Services for SAP SolutionsFixed in: firefox-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Update Services for SAP SolutionsFixed in: thunderbird-0:115.3.1-1.el8_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: thunderbird-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: firefox-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: thunderbird-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: firefox-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: thunderbird-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: firefox-0:115.3.1-1.el8_4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Extended Update SupportFixed in: thunderbird-0:115.3.1-1.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.6 Extended Update SupportFixed in: firefox-0:115.3.1-1.el8_6

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: firefox-0:115.3.1-1.el9_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9Fixed in: thunderbird-0:115.3.1-1.el9_2

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.0 Extended Update SupportFixed in: firefox-0:115.3.1-1.el9_0

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 9.0 Extended Update SupportFixed in: thunderbird-0:115.3.1-1.el9_0

mozillavendor investigatingvia nvd_reference

Vendor Advisories (1)

redhatCVE-2023-5171Important

Mozilla: Use-after-free in Ion Compiler

References

bugzilla.mozilla.org / show_bug.cgi

Issue TrackingPermissions Required

lists.debian.org / debian-lts-announce/2023/09/msg00034.html

Mailing ListPatchThird Party Advisory

lists.debian.org / debian-lts-announce/2023/10/msg00015.html

Mailing ListThird Party Advisory

lists.fedoraproject.org / archives/list/[email protected]/message/AY642Z6JZODQJE7Z62CFREVUHEGCXGPD

Mailing ListThird Party Advisory

debian.org / security/2023/dsa-5506

PatchThird Party Advisory

debian.org / security/2023/dsa-5513

Third Party Advisory

mozilla.org / security/advisories/mfsa2023-41

Vendor Advisory

mozilla.org / security/advisories/mfsa2023-42

Vendor Advisory

mozilla.org / security/advisories/mfsa2023-43

Vendor Advisory