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GHSA-wjfq-88q2-r34j

HighCVSS 7.5 / 10
Published Jan 21, 2022·Last modified Dec 26, 2025
Affected Components(0)

No affected components available

Description

Impact

When handling form responses from the client (ModalFormResponsePacket), the Minecraft Windows client may send weird JSON that json_decode() can't understand. A workaround for this is implemented in InGamePacketHandler::stupid_json_decode().

An InvalidArgumentException is thrown by this function when it fails to fix an error found in the JSON, which is not caught by the caller. This leads to a server crash.

Patches

56fe71d939c38fe14e18a31a673a9331bcc0e4ca

Workarounds

A plugin may handle DataPacketReceiveEvent, capture ModalFormResponsePacket and run the provided JSON through stupid_json_decode.

Note that this requires copying the body of the function to a plugin, since the function is currently private.

For more information

If you have any questions or comments about this advisory:

Risk Scores
Base Score
7.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
6.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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