fastjson: remote code execution

fastjson

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.

Do this now

Check fastjson 1.2.68 to 1.2.83 usage and apply the fixed release when available.

First seen: 23 Oct 2026
Last update: 23 Oct 2026, 19:39 UTC
Identifiers: CVE-2026-16723
CVSS: 9.0
Source: news

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## fastjson: remote code execution
Severity: critical. Patch status: fix status unknown.
Affected: fastjson
Ids: 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.

## Steps
1. Search the repo, its CI and infra config for fastjson. If present, report the version in use and whether it's affected.
2. There is no fix yet. Until one ships: 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.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2026-16723") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://github.com/alibaba/fastjson2/wiki/Security-Advisory:-Remote-Code-Execution-in-fastjson-1.2.68%E2%80%931.2.83 https://nvd.nist.gov/vuln/detail/CVE-2026-16723
https://pwned.coffee/i/a-remote-code-execution-rce-vulnerability-exists-in-fast-cve-2026-16723

Timeline

23 Oct 2026, 19:40 UTC
Proof-of-concept code for CVE-2026-16723 is public on GitHub. Unverified, but expect scanning to follow.
23 Oct 2026
First reported.

Sources

Totalone very hot coffee