CVE-2026-33228
Prototype pollution in flatted JSON parser via __proto__ keys (pre-3.4.2).
Is CVE-2026-33228 being exploited?
Not confirmed. CVE-2026-33228 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.81% probability of exploitation in the next 30 days.
How severe is CVE-2026-33228?
CVE-2026-33228 is rated High with a CVSS score of 8.9. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-33228?
Yes. A fix has been recorded for CVE-2026-33228. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-33228 affect?
CVE-2026-33228 affects flatted <= 3.4.1. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-33228?
Upgrade to 3.4.2+; verify apps and dependencies.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Prototype pollution via JSON parsing; attacker-controlled keys pollute Object.prototype, enabling data tampering and possible RCE.
Patch when possible
- affected< 3.4.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.