What’s Vulnerable › Vulnerabilities

CVE-2021-33790

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-31 · updated 2026-06-17
• Weakness: CWE-502

Description

The RebornCore library before 4.7.3 allows remote code execution because it deserializes untrusted data in ObjectInputStream.readObject as part of reborncore.common.network.ExtendedPacketBuffer. An attacker can instantiate any class on the classpath with any data. A class usable for exploitation might or might not be present, depending on what Minecraft modifications are installed.

Affected products

• Techreborn Reborncore: through 3.13.8; from 3.19.0 before 3.19.5; from 4.2.0 before 4.2.10; from 4.7.0 before 4.7.3 — fixed in 3.19.5, 4.2.10, 4.7.3

How to fix

Upgrade to a fixed version: Techreborn Reborncore 3.19.5, 4.2.10, 4.7.3. Check the vendor advisory for mitigations.

References

• https://github.com/TechReborn/RebornCore/security/advisories/GHSA-r7pg-4xrf-7mrm
• https://vuln.ryotak.me/advisories/45
• https://www.curseforge.com/minecraft/mc-mods/reborncore
• https://github.com/TechReborn/RebornCore/security/advisories/GHSA-r7pg-4xrf-7mrm
• https://vuln.ryotak.me/advisories/45
• https://www.curseforge.com/minecraft/mc-mods/reborncore

Get alerted when CVE-2021-33790 or the next vulnerability affects your stack