CVE-2021-32836Public exploitNetwork attack vector

Pre-auth service crash via arbitrary type deserialization

Published Sep 9, 2021 · Updated Aug 3, 2024

Unsafe deserialization in the ZStack REST API before 3.10.12 and 4.0.0 through 4.1.5 allows remote attackers to crash the service. RESTApiDecoder.loads passes the first request-body key to Class.forName and uses GSON reflection to populate arbitrary fields before casting the object to Message. A reachable unauthenticated API is sufficient for a crash; remote code execution additionally requires a suitable finalization gadget.

CVSS severity8.1
High
EPSS probability2.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe deserialization in the ZStack REST API before 3.10.12 and 4.0.0 through 4.1.5 allows remote attackers to crash the service. RESTApiDecoder.loads passes the first request-body key to Class.forName and uses GSON reflection to populate arbitrary fields before casting the object to Message. A reachable unauthenticated API is sufficient for a crash; remote code execution additionally requires a suitable finalization gadget.

The record

CVE
CVE-2021-32836
Published
Sep 9, 2021
Updated
Aug 3, 2024
Vendor
ZStack
Product
ZStack
Classifications
CWE-502, CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.10.12
  2. Affected versionversion=>= 4.0.0, < 4.1.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ZStack · ZStackversion=< 3.10.12; version=>= 4.0.0, < 4.1.6

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.5GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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