CVE-2021-32827Public exploitNetwork attack vector

Code execution via cross-origin template injection

Published Aug 16, 2021 · Updated Aug 3, 2024

Code injection in MockServer allows remote attackers to execute arbitrary code through cross-origin requests to its REST API. The default CORS policy accepts requests from any origin, while dynamic expectation handlers pass user-supplied JavaScript or Velocity templates to unsandboxed evaluation engines. Exploitation requires a developer running the service to visit an attacker-controlled webpage, which can install and trigger a command-executing expectation.

CVSS severity6.1
Medium
EPSS probability2.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in MockServer allows remote attackers to execute arbitrary code through cross-origin requests to its REST API. The default CORS policy accepts requests from any origin, while dynamic expectation handlers pass user-supplied JavaScript or Velocity templates to unsandboxed evaluation engines. Exploitation requires a developer running the service to visit an attacker-controlled webpage, which can install and trigger a command-executing expectation.

The record

CVE
CVE-2021-32827
Published
Aug 16, 2021
Updated
Aug 3, 2024
Vendor
MockServer
Product
MockServer
Classifications
CWE-79, CWE-74, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 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=all

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MockServer · MockServerversion=all

Published CVSS scores

6.1GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N
9.6NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
6.8NISTAV:N/AC:M/Au:N/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1189Drive-by Compromise

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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