How severe is CVE-2021-33790?

CVE-2021-33790 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-33790 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33790?

CVE-2021-33790 affects Techreborn Reborncore. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33790?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-33790 published?

CVE-2021-33790 was published on 2021-05-31 and last updated on 2026-06-17.

CVE-2021-33790

CVE-2021-33790 is a critical-severity vulnerability in Techreborn Reborncore with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Techreborn Reborncore
Published: 2021-05-31
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-33790?: 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.
How severe is CVE-2021-33790?: CVE-2021-33790 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-33790 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33790?: CVE-2021-33790 affects Techreborn Reborncore. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33790?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-33790 published?: CVE-2021-33790 was published on 2021-05-31 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:techreborn:reborncore:*:*:*:*:*:*:*:*

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