CVE-2026-16723: Input Validation Flaw (CVSS 9)

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.

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CVSS v3.1 Score

9.0

CRITICAL

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0041

Probability of exploitation

0.34%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-502 Deserialization of Untrusted Data

References

Other References

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

Frequently Asked Questions

What is CVE-2026-16723? +

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. It has a CVSS v3.1 base score of 9.0 (CRITICAL).

How severe is CVE-2026-16723? +

CVE-2026-16723 has a CVSS v3.1 score of 9.0 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0041, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-16723? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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