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CVE-2023-6858

24
FAUCET Score

CVE-2023-6858 is a high-severity heap buffer overflow vulnerability in Firefox's nsTextFragment component, stemming from insufficient out-of-memory handling. This flaw impacts Firefox ESR versions prior to 115.6, Thunderbird versions prior to 115.6, and Firefox versions prior to 121. With a CVSS score of 8.8, successful exploitation could lead to high confidentiality, integrity, and availability impacts, requiring user interaction (UI:R) but no authentication (PR:N) over a network (AV:N). Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 121.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 115.6CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
< 115.6CPE 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

8.8HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.53%
Probability of exploitation in next 30 days
EPSS Percentile
72.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0153 is in the 71st percentile among its peer group of 14,875 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.1 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (27)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: thunderbird-0:115.6.0-1.el9_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:115.6.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:115.6.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:115.6.0-1.el8_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:115.6.0-1.el8_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: firefox-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: thunderbird-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Telecommunications Update ServiceFixed in: firefox-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Telecommunications Update ServiceFixed in: thunderbird-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Update Services for SAP SolutionsFixed in: firefox-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Update Services for SAP SolutionsFixed in: thunderbird-0:115.6.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: firefox-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: thunderbird-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: firefox-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Telecommunications Update ServiceFixed in: thunderbird-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: firefox-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Update Services for SAP SolutionsFixed in: thunderbird-0:115.6.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Extended Update SupportFixed in: thunderbird-0:115.6.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Extended Update SupportFixed in: firefox-0:115.6.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Extended Update SupportFixed in: thunderbird-0:115.6.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Extended Update SupportFixed in: firefox-0:115.6.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: thunderbird-0:115.6.0-1.el9_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: firefox-0:115.6.0-1.el9_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.0 Extended Update SupportFixed in: thunderbird-0:115.6.0-1.el9_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.0 Extended Update SupportFixed in: firefox-0:115.6.0-1.el9_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: firefox-0:115.6.0-1.el9_2
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (2)

redhatCVE-2023-6858Moderate

Mozilla: Heap buffer overflow in <code>nsTextFragment</code>

Dec 19, 2023
microsoft2023-Dec/CVE-2023-6858Important

Firefox was susceptible to a heap buffer overflow in `nsTextFragment` due to insufficient OOM handling. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

Dec 12, 2023

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions Required
lists.debian.org / debian-lts-announce/2023/12/msg00020.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2023/12/msg00021.html
Mailing ListThird Party Advisory
security.gentoo.org / glsa/202401-10
Third Party Advisory
debian.org / security/2023/dsa-5581
Third Party Advisory
debian.org / security/2023/dsa-5582
Third Party Advisory
mozilla.org / security/advisories/mfsa2023-54
Vendor Advisory
mozilla.org / security/advisories/mfsa2023-55
Vendor Advisory
mozilla.org / security/advisories/mfsa2023-56
Vendor Advisory