What is CVE-2019-11707?

CVE-2019-11707 is a high-severity vulnerability in Mozilla Firefox, classified under Access of Resource Using Incompatible Type (Type Confusion). CVSS score: 8.8/10. Published 2019-07-23.

How severe is CVE-2019-11707?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2019-11707 known to be exploited?

Yes. CVE-2019-11707 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-05-23), indicating it is being actively exploited. 31 public proof-of-concept repositories are indexed.

Vulnerability in Mozilla Firefox

CVE-2019-11707

A type confusion vulnerability can occur when manipulating JavaScript objects due to issues in Array.pop. This can allow for an exploitable crash. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 60.7.1, Firefox < 67.0.3, and Thunderbird < 60.7.2.

Published 2019-07-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.377 (98.5th percentile), scored 2026-10-19.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 99th percentile — 98.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.377 · newest: 0.377 · change: 0.000

Affected products

Mozilla Firefox — versions unspecified
Mozilla Firefox Esr — versions unspecified
Mozilla Thunderbird — versions unspecified

Weakness classification (CWE)

CWE-843 — Access of Resource Using Incompatible Type (Type Confusion)

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-05-23. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-06-13.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

www.mozilla.org/security/advisories/mfsa2019-20/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2019-18/ (Vendor Advisory)
bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking, Vendor Advisory)
security.gentoo.org/glsa/201908-12 (vendor-advisory, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2019-11707?: CVE-2019-11707 is a high-severity vulnerability in Mozilla Firefox, classified under Access of Resource Using Incompatible Type (Type Confusion). CVSS score: 8.8/10. Published 2019-07-23.
How severe is CVE-2019-11707?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2019-11707 known to be exploited?: Yes. CVE-2019-11707 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-05-23), indicating it is being actively exploited. 31 public proof-of-concept repositories are indexed.