CVE-2021-32836: Pre-auth unsafe deserialization in ZStack

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.0% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-09-09 · updated 2026-06-17
Weakness: CWE-94

Description

ZStack is open source IaaS(infrastructure as a service) software. In ZStack before versions 3.10.12 and 4.1.6 there is a pre-auth unsafe deserialization vulnerability in the REST API. An attacker in control of the request body will be able to provide both the class name and the data to be deserialized and therefore will be able to instantiate an arbitrary type and assign arbitrary values to its fields. This issue may lead to a Denial Of Service. If a suitable gadget is available, then an attacker may also be able to exploit this vulnerability to gain pre-auth remote code execution. For additional details see the referenced GHSL-2021-087.

Affected products

zstackio zstack: before 3.10.12; from 4.1.0 before 4.1.6 — fixed in 3.10.12, 4.1.6

How to fix

Upgrade to a fixed version: zstackio zstack 3.10.12, 4.1.6. Check the vendor advisory for mitigations.

References

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