CAPEC-271
Schema Poisoning
An adversary corrupts or modifies the content of a schema for the purpose of undermining the security of the target. Schemas provide the structure and content definitions for resources used by an application. By replacing or modifying a schema, the adversary can affect how the application handles or interprets a resource, often leading to possible denial of service, entering into an unexpected state, or recording incomplete data.
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Explain the attack pattern CAPEC-271: Schema Poisoning: how it unfolds, what it needs and how to prevent and detect it in my systems. Use https://capec.mitre.org/data/definitions/271.html and https://cve.bz/cve/capec/271?via=ask-ai-copy, which lists recent CVEs with the weaknesses it exploits. Cite the sources.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this attack pattern's id and public links.
How the attack unfolds
Explore
The attacker looks for a way in.
[Find target application and schema] The adversary first finds the application that they want to target. This application must use schemas in some way, so the adversary also needs to confirm that schemas are being used.
2 techniques
- Gain access to the system that the application is on and look for a schema.
- Observe HTTP traffic to the application and look for a schema being transmitted.
Experiment
They probe what they found.
[Gain access to schema] The adversary gains access to the schema so that they can modify the contents.
2 techniques
- For a local scenario, the adversary needs access to the machine that the schema is located on and gain permissions to alter the contents of the schema file.
- For a remote scenario, the adversary needs to be able to perform an adversary in the middle attack on the HTTP traffic that contains a schema.
Exploit
They carry out the attack.
[Poison schema] Once the adversary gains access to the schema, they will alter it to achieve a desired effect. Locally, they can just modify the file. For remote schemas, the adversary will alter the schema in transit by performing an adversary in the middle attack.
3 techniques
- Cause a denial of service by modifying the schema so that it does not contain required information for subsequent processing.
- Manipulation of the data types described in the schema may affect the results of calculations. For example, a float field could be changed to an int field.
- Change the encoding defined in the schema for certain fields allowing the contents to bypass filters that scan for dangerous strings. For example, the modified schema might use a URL encoding instead of ASCII, and a filter that catches a semicolon (;) might fail to detect its URL encoding (%3B).
Prerequisites
Some level of access to modify the target schema.
The schema used by the target application must be improperly secured against unauthorized modification and manipulation.
Resources required
Access to the schema and the knowledge and ability modify it. Ability to replace or redirect access to the modified schema.
Consequences
| Impact | Affects | Note |
|---|---|---|
| Unreliable Execution, Resource Consumption | Availability | A successful schema poisoning attack can compromise the availability of the target system's service by exhausting its available resources. |
| Modify Data | Integrity | |
| Read Data | Confidentiality |
Mitigations
Design: Protect the schema against unauthorized modification.
Implementation: For applications that use a known schema, use a local copy or a known good repository instead of the schema reference supplied in the schema document.
Implementation: For applications that leverage remote schemas, use the HTTPS protocol to prevent modification of traffic in transit and to avoid unauthorized modification.
Weaknesses it exploits
- CWE-15 External Control of System or Configuration Setting
Recent CVEs with these weaknesses
- 8.8CVE-2026-13292
IBM MQ 9.2.0.0 through 9.2.0.44 LTS, 9.3.0.0 through 9.3.0.42 LTS, 9.4.0.0 through 9.4.0.26 LTS, 9.4.0.0 through 9.4.5.1 CD, and 10.0.0.0 through 10.0.0.5 LTS and CD could allow an authenticated attacker to execute arbitrary code by inject…
- 7.1CVE-2026-121614
Docker Sandboxes versions 0.31.0 before 0.50.0 do not neutralize repository-controlled Git configuration when running certain host-side Git commands. An attacker who can modify a host repository's Git configuration, for example through a d…
- 8.7CVE-2026-121427
AzuraCast through 0.23.8 fails to remove frontend_config.custom_config in PUT /station/{id}/profile/edit for users lacking the Manage station broadcasting permission, and the stored JSON is written verbatim as key=value lines into the Shou…
- 4.6CVE-2025-68403
An external control of system or configuration setting vulnerability has been reported to affect QuRouter. If a local attacker gains an administrator account, they can then exploit the vulnerability to modify data on the system. We have a…
- 7.7CVE-2026-110845
n8n before 1.123.83, 2.x before 2.41.4, and 2.42.x before 2.42.1 contains a code execution vulnerability in the Git node Log operation, which fails to strip a repository's local git configuration before invoking an external program. Authen…
- 5.5CVE-2026-96218
Improper access control in Windows Update Stack allows an authorized attacker to perform tampering locally.
- 7.3CVE-2026-96188
External control of system or configuration setting in Microsoft PowerToys allows an authorized attacker to elevate privileges locally.
- 7.8CVE-2026-73027
External control of system or configuration setting in Windows Setup Files Cleanup allows an authorized attacker to elevate privileges locally.
The newest records naming one of them. Each weakness's page lists them all.
Related attack patterns
- Part of
- CAPEC-176 Configuration/Environment Manipulation
- Can follow
- CAPEC-94 Adversary in the Middle (AiTM)
- More specific patterns
- CAPEC-146 XML Schema Poisoning
Examples
In a JSON Schema Poisoning Attack, an adervary modifies the JSON schema to cause a Denial of Service (DOS) or…
In a JSON Schema Poisoning Attack, an adervary modifies the JSON schema to cause a Denial of Service (DOS) or to submit malicious input:
{ "title": "Contact", "type": "object", "properties": { "Name": { "type": "string" }, "Phone": { "type": "string" }, "Email": { "type": "string" }, "Address": { "type": "string" } }, "required": ["Name", "Phone", "Email", "Address"] }
If the 'name' attribute is required in all submitted documents and this field is removed by the adversary, the application may enter an unexpected state or record incomplete data. Additionally, if this data is needed to perform additional functions, a Denial of Service (DOS) may occur.
In a Database Schema Poisoning Attack, an adversary alters the database schema being used to modify the datab…
In a Database Schema Poisoning Attack, an adversary alters the database schema being used to modify the database in some way. This can result in loss of data, DOS, or malicious input being submitted. Assuming there is a column named "name", an adversary could make the following schema change:
ALTER TABLE Contacts MODIFY Name VARCHAR(65353);
The "Name" field of the "Conteacts" table now allows the storing of names up to 65353 characters in length. This could allow the adversary to store excess data within the database to consume system resource or to execute a DOS.
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