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CVE-2026-16723

Remote Code Execution in fastjson 1.2.68–1.2.83

Published: Jul 23, 2026Updated: Jul 23, 2026 Sources: CVE List NVDCWE-20
9.0CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 65.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

Description

A remote code execution (RCE) vulnerability exists in fastjson 1.2.68 through 1.2.83. This vulnerability is exploitable under fastjson's stock default configuration — no AutoType enablement required, no classpath gadget required.

In plain language

AI Act now

CVE-2026-16723 is a serious remote code execution flaw in Fastjson 1.2.68–1.2.83, and typical small businesses should treat it as urgent if they run software that uses this exact Fastjson version (it’s being exploited in the wild).

Executive summary

CVE-2026-16723 is an unauthenticated remote code execution issue in Fastjson (versions 1.2.68 through 1.2.83) triggered by crafted JSON input that abuses how the library processes certain data, and it is exploitable under Fastjson’s default configuration without AutoType enablement or classpath gadgets.

If affected, business impact
Full server takeoverMalware installationCustomer/employee data theftService disruption

What to do now

  1. Check where Fastjson is used (your app, plugins, or dependencies) and confirm the Fastjson version is between 1.2.68 and 1.2.83.
  2. If you are on 1.2.68–1.2.83, stop taking untrusted JSON inputs through that Fastjson code path immediately (block the endpoints, or temporarily disable features that parse attacker-controlled JSON).
  3. Remove Fastjson from the affected component(s) by upgrading to a Fastjson release outside 1.2.68–1.2.83; if no fixed version is available for your stack, replace the JSON library used by your application.
  4. Hunt for active exploitation by reviewing application and system logs for evidence of unusual JSON payloads and unexpected process/network activity after JSON parsing.
May need vendor / contractor work

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:CC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-20CWE-502

Affected Products

Alibaba
commercial·CNaka nacos, fastjson
FastjsonMixed
OSS Libraries / generic-library

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
Is your org exposed to CVE-2026-16723?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes for MITRE ATT&CK details · drag to pan · Ctrl/⌘ + scroll to zoom, or go fullscreen.

MITRE ATT&CK

3 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/alibaba/fastjson2/wiki/Security-Advisory:-Remote-Code-Execution-in-fastjson-1.2.68%E2%80%931.2.83
github.com
News mentions
7

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