Fastjson Strikes Again: A Nuclear‑Grade Vulnerability Exposes Critical Risks

A Late “Nuclear” Bomb

On July 19, 2026, security researcher Kirill Firsov disclosed a remote code execution (RCE) vulnerability in the last Fastjson 1.x releases (1.2.68–1.2.83) that can be triggered without any gadget chain. The affected versions include the officially declared “final safe version” 1.2.83. The vulnerability works with default configuration; disabling autoType or binding concrete types does not mitigate it. CVSS 9.8, exploitable in Spring Boot FatJar + JDK 8 environments. A proof‑of‑concept was published on GitHub the next day. Affected versions: 1.2.66–1.2.83 (including 1.2.83) Exploitation condition: default config, autoType cannot be disabled, binding specific type ineffective Severity: CVSS 9.8, RCE in typical Spring Boot + JDK 8 setups POC released: public on GitHub within a day

Fastjson 1.x stopped maintenance in 2024; the last official release was in 2022. Although many projects still rely on it, the library has been effectively abandoned.

Double‑Standard Fallout

After the disclosure, various tech communities, chat groups, and cloud providers reacted with a flood of criticism. Sample high‑up‑vote comments illustrate the frustration, ranging from “Why are we still using this junk?” to “Alibaba, how can you release such irresponsible code?”

Some developers wrote scripts to scan dependencies, others enabled SafeMode as a stop‑gap, while many continued to use 1.2.83 waiting for a patch that is unlikely to appear because the maintainers have announced only security‑only maintenance and recommend migration to Fastjson 2.x.

The Scariest Attitude

The author argues that the worst problem is the “wait‑and‑expect‑someone‑else‑to‑fix” mindset combined with personal attacks. Open‑source software is free and under an Apache license; users receive no SLA or 24/7 support. Responsibility for fixing bugs lies with the community, not the original authors.

Open‑Source Free‑Rider Dilemma

The situation exemplifies the classic free‑rider problem: public resources require maintenance costs, yet many users expect others to bear those costs. Fastjson’s original authors invested years maintaining the library, fixing countless bugs, and eventually shifted effort to the redesigned Fastjson 2.x.

Community responses include concerns about migration cost, technical debt, and the lack of a commercial‑grade support model for free software.

What Mature Programmers Should Do

Accept that open‑source does not imply unlimited responsibility; do not treat maintainers as an outsourced team.

Pay down technical debt early; debt compounds over time.

Develop a supply‑chain security mindset for third‑party libraries.

Participate in the community: file issues, star projects, write blogs, or submit pull requests.

Those who only complain without taking action become the biggest drain on the open‑source ecosystem.

Conclusion

The Fastjson 1.x vulnerability is both a technical and community problem. Critiquing its design, discussing security culture, and urging enterprises to support open‑source maintainers are valuable. Constructive discussion is welcome; personal attacks are not. The open‑source spirit is “we improve together,” and action outweighs mere criticism.