No exploitation reportedFix available

CVE-2020-15669

Q: Is CVE-2020-15669 actively exploited?

Active exploitation of CVE-2020-15669 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-15669?

CVE-2020-15669 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2020-10-01
Fixed in68.12
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

When aborting an operation, such as a fetch, an abort signal may be deleted while alerting the objects to be notified. This results in a use-after-free and we presume that with enough effort it could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.12 and Thunderbird < 68.12.

Timeline

dates in UTC

2020-10-0119:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 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-2020-15669?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-15669?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Mozilla firefox esr

Branch	Affected	Fixed in	Source
68.12	< 68.12	68.12	NVD

Mozilla thunderbird

Branch	Affected	Fixed in	Source
68.12	< 68.12	68.12	NVD

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

Fix

Update Mozilla firefox esr to 68.12

Advisories and patches

bugzilla.mozilla.orgVendor Advisory
www.mozilla.orgRelease Notes · Vendor Advisory
www.mozilla.orgRelease Notes · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.18.8read 2026-10-23
NVDCVSS 2.06.8read 2026-10-23
NVDweakness (CWE)CWE-416read 2026-10-23
FIRST EPSSEPSS score1.1 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published: 2020-10-01
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-15669?

Is CVE-2020-15669 actively exploited?

Active exploitation of CVE-2020-15669 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-15669?

CVE-2020-15669 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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