fastjson is a widely used Java JSON library; unauthenticated RCE via default config can compromise many enterprise apps and services.
CVE-2026-16723
Unauthenticated RCE in fastjson 1.2.68–1.2.83 via default configuration (no AutoType).
Is CVE-2026-16723 being exploited?
Not confirmed. CVE-2026-16723 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 16% probability of exploitation in the next 30 days.
How severe is CVE-2026-16723?
CVE-2026-16723 is rated Critical. 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-2026-16723?
Yes. A fix has been recorded for CVE-2026-16723. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16723 affect?
CVE-2026-16723 affects Alibaba fastjson 1.2.68 - 1.2.83, Java applications and services using fastjson library. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16723?
Upgrade fastjson to the fixed release; else replace library or block/validate untrusted JSON.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated remote code execution: attacker-supplied JSON can execute arbitrary Java code, enabling data theft, persistence, and full system compromise.
Immediate action required
- affected>= 1.2.68 and <= 1.2.83
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.