CVE-2019-9813

Status: ModifiedHigh (8.8)—💥 Exploit

Incorrect handling of __proto__ mutations may lead to type confusion in IonMonkey JIT code and can be leveraged for arbitrary memory read and write. This vulnerability affects Firefox < 66.0.1, Firefox ESR < 60.6.1, and Thunderbird < 60.6.1.

CVSS

Version: 3.0
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Base score: 8.8

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 7.39%
Percentile among all scored CVEs: 94
Score date: 10/9/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

💥 Public exploits

Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.

Published on Exploit-DB · SpiderMonkey - IonMonkey Compiled Code Fails to Update Inferred Property Types (Type Confusion) (4/3/2019)

Affected technologies (2)

Mozilla — Firefox Mozilla — Thunderbird

CWEs

CWE-843

References

Raw JSON (NVD)

Show

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