Public proof of concept

CVE-2018-18500

Q: Is CVE-2018-18500 actively exploited?

Active exploitation of CVE-2018-18500 has not been confirmed. Its EPSS score was 12.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2018-18500?

CVE-2018-18500 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2019-02-05
WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A use-after-free vulnerability can occur while parsing an HTML5 stream in concert with custom HTML elements. This results in the stream parser object being freed while still in use, leading to a potentially exploitable crash. This vulnerability affects Thunderbird < 60.5, Firefox ESR < 60.5, and Firefox < 65.

Timeline

dates in UTC

2019-02-0521:29CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2018-18500?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2018-18500?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Canonical ubuntu linux

Branch	Affected	Fixed in	Source
14.4	= 14.04	no fix published	NVD
16.4	= 16.04	no fix published	NVD
18.4	= 18.04	no fix published	NVD
18.10	= 18.10	no fix published	NVD

Debian debian linux

Branch	Affected	Fixed in	Source
8.0	= 8.0	no fix published	NVD
9.0	= 9.0	no fix published	NVD

Redhat enterprise linux desktop

Branch	Affected	Fixed in	Source
6.0	= 6.0	no fix published	NVD
7.0	= 7.0	no fix published	NVD

8 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

www.mozilla.orgVendor Advisory
www.mozilla.orgVendor Advisory
www.mozilla.orgVendor Advisory

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedsophoslabs/CVE-2018-18500

Sources

NVDCVSS 3.09.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
NVDweakness (CWE)CWE-416read 2026-10-23
FIRST EPSSEPSS score12.7 %read 2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2019-02-05
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2018-18500?

Is CVE-2018-18500 actively exploited?

Active exploitation of CVE-2018-18500 has not been confirmed. Its EPSS score was 12.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2018-18500?

CVE-2018-18500 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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