Is CVE-2023-6858 in the CISA KEV catalog?

No. CVE-2023-6858 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2023-6858?

CVE-2023-6858 has a CVSS v3 base score of 8.8 (HIGH).

What is the EPSS score for CVE-2023-6858?

CVE-2023-6858 has an EPSS score of 1.53% (72th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2023-6858?

Upgrade firefox on debian unstable to 121.0-1 or later. Fixes are available for 21 affected products.

CVE & CISA-KEV Catalog

CVE-2023-6858

HIGHEPSS 72th pctl

8.8

CVSS v3

NVD

Description

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.

CWE-787Out-of-bounds Write

How to fix

Remediation Available

firefoxDebian

Fixed in:121.0-1CVE-2023-6858

firefoxRocky

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9.ppc64RHSA-2024:0026

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

firefoxRed Hat / RHEL

Fixed in:0:115.6.0-1.el7_9.ppc64RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

firefox-debuginfoRocky

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9.ppc64RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

firefox-debuginfoRed Hat / RHEL

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9.ppc64RHSA-2024:0026

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0026

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

firefox-debugsourceRocky

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

firefox-debugsourceRed Hat / RHEL

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0023

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0024

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0012

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0011

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0021

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0022

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

firefox-x11Red Hat / RHEL

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

firefox-x11Rocky

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0025

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0019

thunderbirdRocky

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0027

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

thunderbirdRed Hat / RHEL

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0027

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

thunderbird-debuginfoRed Hat / RHEL

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0027

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

thunderbird-debuginfoRocky

Fixed in:0:115.6.0-1.el7_9RHSA-2024:0027

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

thunderbird-debugsourceRocky

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

thunderbird-debugsourceRed Hat / RHEL

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_8RHSA-2024:0004

Fixed in:0:115.6.0-1.el8_4RHSA-2024:0028

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_2RHSA-2024:0030

Fixed in:0:115.6.0-1.el8_6RHSA-2024:0005

Fixed in:0:115.6.0-1.el8_9RHSA-2024:0003

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_2RHSA-2024:0029

Fixed in:0:115.6.0-1.el9_3RHSA-2024:0001

Fixed in:0:115.6.0-1.el9_0RHSA-2024:0002

firefoxUbuntu

Fixed in:121.0+build1-0ubuntu0.20.04.1USN-6562-1

thunderbirdUbuntu

Fixed in:1:115.6.0+build2-0ubuntu0.20.04.1USN-6563-1

Fixed in:1:115.6.0+build2-0ubuntu0.22.04.1USN-6563-1

Fixed in:1:115.6.0+build2-0ubuntu0.23.04.1USN-6563-1

Fixed in:1:115.6.0+build2-0ubuntu0.23.10.1USN-6563-1

DeveloperEditionWindows application

Affected:121.0Fixed in:121.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:121.0Fixed in:121.0Mozilla

Mozilla Firefox ESR (en-US)Windows application

Affected:115.6Fixed in:115.6Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:115.6Fixed in:115.6Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

1.53%probability of exploitation in 30 days

72ndpercentile

Elevated risk: more likely to be exploited than 72% of all known CVEs.

References

Vendor Advisory3

Third-Party Advisory5

Issue Tracking1

bugzilla.mozilla.org

Related Vulnerabilities

Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2023-4863	High	8.8	100%	KEV	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-05-07.