LiveActive security incident?Get immediate response
CVE Record

CVE-2021-33790: The RebornCore library before 4.7.3 allows remote code execution because it deserializes untrusted data in...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-33790 is a remote code execution risk in RebornCore before 4.7.3, a Minecraft mod library. It processes untrusted serialized data in a way that may let an attacker create arbitrary classes on the Java classpath. Practical impact depends on which other Minecraft mods are installed.

Executive priority

Treat as high priority where RebornCore is used on reachable modded Minecraft services. The business urgency is lower for isolated or non-production modpacks, but RCE potential warrants prompt inventory and upgrade.

Technical view

The issue is unsafe Java deserialization through ObjectInputStream.readObject in reborncore.common.network.ExtendedPacketBuffer. Sources state an attacker can instantiate any class on the classpath with supplied data. Exploitability may require a suitable class from installed mods or dependencies.

Likely exposure

Exposure is most likely in modded Minecraft environments using RebornCore versions before 4.7.3. Risk varies by deployment, network reachability, and whether installed mods provide classes useful for exploitation.

Exploitation context

No provided source and no KEV flag indicate known active exploitation. The sources describe a conditionally exploitable RCE primitive, where usable exploit paths depend on the runtime classpath.

Researcher notes

Evidence identifies unsafe deserialization and arbitrary class instantiation, but does not provide CVSS, CWE, affected CPEs, or confirmed exploitation. Classpath-dependent exploitability is the key uncertainty for validation.

Mitigation direction

  • Upgrade RebornCore to version 4.7.3 or later.
  • Check the GitHub advisory and CurseForge page for current vendor guidance.
  • Remove or disable affected RebornCore deployments if upgrade is not feasible.
  • Limit untrusted access to affected modded Minecraft services.

Validation and detection

  • Inventory servers, clients, and modpacks for RebornCore versions before 4.7.3.
  • Review installed Minecraft mods and dependencies for classpath exposure context.
  • Confirm updated deployments no longer include vulnerable RebornCore versions.
  • Check vendor advisory status before accepting residual risk.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-33790 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.