Is CVE-2018-5099 in the CISA KEV catalog?

No. CVE-2018-5099 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2018-5099?

CVE-2018-5099 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2018-5099?

CVE-2018-5099 has an EPSS score of 3.07% (86th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2018-5099?

Upgrade firefox on debian unstable to 58.0-1 or later. Fixes are available for 6 affected products.

CVE & CISA-KEV Catalog

CVE-2018-5099

CRITICALEPSS 86th pctl

9.8

CVSS v3

NVD

Description

A use-after-free vulnerability can occur when the widget listener is holding strong references to browser objects that have previously been freed, resulting in a potentially exploitable crash when these references are used. This vulnerability affects Thunderbird < 52.6, Firefox ESR < 52.6, and Firefox < 58.

CWE-416Use After Free

How to fix

Remediation Available

firefoxDebian

Fixed in:58.0-1CVE-2018-5099

firefoxUbuntu

Fixed in:58.0+build6-0ubuntu0.14.04.1USN-3544-1

Fixed in:58.0+build6-0ubuntu0.16.04.1USN-3544-1

thunderbirdUbuntu

Fixed in:1:52.6.0+build1-0ubuntu0.14.04.1USN-3529-1

Fixed in:1:52.6.0+build1-0ubuntu0.16.04.1USN-3529-1

DeveloperEditionWindows application

Affected:52.6.0Fixed in:52.6.0Mozilla

Affected:58.0Fixed in:58.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:52.6.0Fixed in:52.6.0Mozilla

Affected:58.0Fixed in:58.0Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:52.6.0Fixed in:52.6.0Mozilla

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 InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

3.07%probability of exploitation in 30 days

86thpercentile

Elevated risk: more likely to be exploited than 86% of all known CVEs.

References

Vendor Advisory3

Third-Party Advisory10

Related Vulnerabilities

Other CWE-416 (Use After Free) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2019-0708	Critical	9.8	100%	KEV + Ransom	-
CVE-2021-31166	Critical	9.8	100%	KEV	Fix
CVE-2015-5119	Critical	9.8	99%	KEV	-
CVE-2010-3962	High	8.1	97%	KEV	-
CVE-2015-0313	Critical	9.8	96%	KEV	Fix
CVE-2017-9798	High	7.5	95%	-	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 2025-11-25.