CVE-2023-6863

HIGHNVD 8.88.8—

8.8

The ShutdownObserver() was susceptible to potentially undefined behavior due to its reliance on a dynamic type that lacked a virtual destructor. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

CVSS v3: 8.8
EG Score: 8.8(medium)
EPSS: 59.5%
KEV: Not listed

Published

December 19, 2023

Last Modified

June 17, 2026

References (14)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1868901
security@mozillahttps://lists.debian.org/debian-lts-announce/2023/12/msg00020.html
security@mozillahttps://security.gentoo.org/glsa/202401-10
security@mozillahttps://www.debian.org/security/2023/dsa-5581
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2023-54/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2023-55/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2023-56/
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.mozilla.org/show_bug.cgi?id=1868901
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2023/12/msg00020.html
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202401-10
af854a3a-2127-422b-91ae-364da2661108https://www.debian.org/security/2023/dsa-5581
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2023-54/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2023-55/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2023-56/

Patch Availability(20)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	xul-ext-lightning (1:115.6.0+build2-0ubuntu0.20.04.1) @ focal	2026-05-24	ubuntu
ubuntu	firefox-mozsymbols (121.0+build1-0ubuntu0.20.04.1) @ focal	2026-05-24	ubuntu
redhat	thunderbird-0:115.6.0-1.el8_4	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el8_6	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el8_8	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el8_2	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el9_2	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el9_3	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el8_9	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el9_0	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el9_3	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el8_2	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el8_4	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el8_8	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el9_0	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el9_2	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el7_9	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el7_9	2024-01-02	redhat
redhat	thunderbird-0:115.6.0-1.el8_9	2024-01-02	redhat
redhat	firefox-0:115.6.0-1.el8_6	2024-01-02	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

All Vendor Advisories

(20)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-23 21:31 UTCEPSS rescore
2026-06-23 21:31 UTCEPSS rescore
2026-06-22 14:24 UTCEPSS rescore
2026-06-22 14:24 UTCEPSS rescore
2026-06-21 14:55 UTCEPSS rescore
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2026-06-21 01:58 UTCEPSS rescore
2026-06-21 01:58 UTCEPSS rescore
2026-06-19 19:24 UTCEPSS rescore
2026-06-19 19:24 UTCEPSS rescore
2026-06-18 17:51 UTCEPSS rescore
2026-06-17 17:51 UTCEPSS rescore
2026-06-16 17:51 UTCEPSS rescore
2026-06-16 17:51 UTCEPSS rescore
2026-06-15 17:47 UTCEPSS rescore
2026-06-14 23:16 UTCEPSS rescore
2026-06-13 22:59 UTCEPSS rescore
2026-06-13 22:59 UTCEPSS rescore
2026-06-12 23:11 UTCEPSS rescore
2026-06-11 13:59 UTCEPSS rescore
2026-06-10 22:17 UTCEPSS rescore
2026-06-10 13:21 UTCEPSS rescore
2026-06-09 11:58 UTCOSV refresh
2026-06-08 14:16 UTCEPSS rescore
2026-06-08 14:16 UTCEPSS rescore

Show 28 more

2026-06-07 15:24 UTCEPSS rescore
2026-06-07 15:24 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-05 22:46 UTCEPSS rescore
2026-06-05 22:46 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-04 13:11 UTCEPSS rescore
2026-06-04 13:11 UTCEPSS rescore
2026-06-02 20:12 UTCEPSS rescore
2026-06-02 20:12 UTCEPSS rescore
2026-05-31 22:30 UTCEPSS rescore
2026-05-31 22:30 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-29 13:43 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-27 13:40 UTCEPSS rescore
2026-05-27 13:39 UTCEPSS rescore
2026-05-26 13:43 UTCEPSS rescore
2026-05-26 13:43 UTCEPSS rescore
2026-05-26 07:18 UTCEPSS rescore
2026-05-26 07:18 UTCEPSS rescore
2026-05-24 11:46 UTCEG score recompute
2026-05-24 11:46 UTCVendor advisory
2026-05-24 11:46 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2023-6863?

CVE-2023-6863 is a high vulnerability published on December 19, 2023. The ShutdownObserver() was susceptible to potentially undefined behavior due to its reliance on a dynamic type that lacked a virtual destructor. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

When was CVE-2023-6863 disclosed?

CVE-2023-6863 was first published in the National Vulnerability Database on December 19, 2023, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2023-6863 actively exploited?

CVE-2023-6863 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 59.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2023-6863?

CVE-2023-6863 has a CVSS v3 base score of 8.8 (NVD).

How do I remediate CVE-2023-6863?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-6863, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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