CVE-2019-17026 — Mozilla
HIGHCVE-2019-17026 is a high-severity (CVSS 8.8) CWE-843 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2022-05-03.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2019-17026.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2019-17026 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 68.4.1, Thunderbird < 68.4.1, and Firefox < 72.0.1.
Affected Products
ubuntu linuxcanonicalfirefoxmozillathunderbirdmozillaResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Firefox 72 IonMonkey - JIT Type Confusion
by Forrest Orr · May 13, 2021
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2019-17026 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 6 | firefox-0:68.4.1-1.el6_10 | RHSA-2020:0086 |
| Red Hat Enterprise Linux 6 | thunderbird-0:68.4.1-2.el6_10 | RHSA-2020:0123 |
| Red Hat Enterprise Linux 7 | firefox-0:68.4.1-1.el7_7 | RHSA-2020:0085 |
| Red Hat Enterprise Linux 7 | thunderbird-0:68.4.1-2.el7_7 | RHSA-2020:0120 |
| Red Hat Enterprise Linux 8 | firefox-0:68.4.1-1.el8_1 | RHSA-2020:0111 |
| Red Hat Enterprise Linux 8 | thunderbird-0:68.4.1-2.el8_1 | RHSA-2020:0127 |
| Red Hat Enterprise Linux 8.0 Update Services for SAP Solutions | thunderbird-0:68.4.1-2.el8_0 | RHSA-2020:0292 |
| Red Hat Enterprise Linux 8.0 Update Services for SAP Solutions | firefox-0:68.4.1-1.el8_0 | RHSA-2020:0295 |
Frequently Asked Questions
Is CVE-2019-17026 in your dependencies?
Find it across , including transitive dependencies.