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Vulnerabilities

Vulnerability · CVE-2019-17026

Mozilla Firefox And Thunderbird Type Confusion Vulnerability

Published Jan 7, 2020 · catalog updated Jun 16, 2026 · Mozilla Firefox and Thunderbird

Patch now

CVE-2019-17026 is in the CISA known-exploited catalog, due May 3, 2022. Confirm Mozilla Firefox and Thunderbird against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
High8.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
46.31%
Remediation
Remediation guidance
Affected products
cpe canonical/ubuntu linux · cpe mozilla/firefox · cpe mozilla/thunderbird · vendor Mozilla Firefox and Thunderbird

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe canonical/ubuntu linux16.04
  • cpe mozilla/firefoxversion unspecified
  • cpe mozilla/thunderbirdversion unspecified
  • vendor Mozilla Firefox and Thunderbirdversion unspecified

How to fix CVE-2019-17026

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2019-17026 is in the CISA known-exploited catalog, due May 3, 2022. Confirm Mozilla Firefox and Thunderbird against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with canonical/ubuntu linux 16.04. Apply updates per vendor instructions.

What should an analyst verify?

CWE-843: Access of Resource Using Incompatible Type (Type Confusion). EPSS 46.31%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 1, 2020 · Catalog

    Detected

    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.

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 3, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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.

Sources

  • CISA KEVConfirmed exploitationCVE-2019-17026

    Mozilla Firefox and Thunderbird contain a type confusion vulnerability due to incorrect alias information in the IonMonkey JIT compiler when setting array elements.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2019-17026

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2019-17026

    30-day exploitation probability 46.3%

    first.org
  • Exploit DatabasePublic exploit reference49864

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • NIST NVDVulnerability recordCVE-2019-17026

    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.

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/162568/Firefox-72-IonMonkey-JIT-Type-Confusion.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-2019-17026

    Mozilla Firefox and Thunderbird contain a type confusion vulnerability due to incorrect alias information in the IonMonkey JIT compiler when setting array elements.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.