Package Instance

Jenkins JUnit Plugin subject to Cross-site Scripting via URL conversion
JUnit Plugin 1159.v0b_396e1e07dd and earlier converts HTTP(S) URLs in test report output to clickable links.

This is done in an unsafe manner, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with Item/Configure permission.

JUnit Plugin 1160.vf1f01a_a_ea_b_7f no longer converts URLs to clickable links.

Sandbox bypass vulnerability in Jenkins Pipeline: Deprecated Groovy Libraries Plugin
Pipeline: Groovy Libraries Plugin and older releases of the Pipeline: Deprecated Groovy Libraries Plugin (formerly Pipeline: Shared Groovy Libraries Plugin) define the l`ibrary` Pipeline step, which allows Pipeline authors to dynamically load Pipeline libraries. The return value of this step can be used to instantiate classes defined in the loaded library.

In Pipeline: Groovy Libraries Plugin 612.v84da_9c54906d and earlier and in Pipeline: Deprecated Groovy Libraries Plugin 583.vf3b_454e43966 and earlier, the `library` step can be used to invoke sandbox-generated synthetic constructors in crafted untrusted libraries and construct any subclassable type. This is similar to SECURITY-582 in the [2017-08-07 security advisory](https://www.jenkins.io/security/advisory/2017-08-07/#multiple-groovy-language-features-allowed-script-security-plugin-sandbox-bypass), but in a different plugin.

This vulnerability allows attackers with permission to define untrusted Pipeline libraries and to define and run sandboxed Pipelines, to bypass the sandbox protection and execute arbitrary code in the context of the Jenkins controller JVM.

Pipeline: Groovy Libraries Plugin 613.v9c41a_160233f rejects improper calls to sandbox-generated synthetic constructors when using the `library` step.

Pipeline: Deprecated Groovy Libraries Plugin 588.v576c103a_ff86 no longer contains the `library` step. It has been moved into the Pipeline: Groovy Libraries Plugin.

Sandbox bypass vulnerability in Jenkins Pipeline: Groovy Libraries Plugin and Pipeline: Deprecated Groovy Libraries Plugin
Pipeline: Groovy Libraries Plugin and older releases of the Pipeline: Deprecated Groovy Libraries Plugin (formerly Pipeline: Shared Groovy Libraries Plugin) define the l`ibrary` Pipeline step, which allows Pipeline authors to dynamically load Pipeline libraries. The return value of this step can be used to instantiate classes defined in the loaded library.

In Pipeline: Groovy Libraries Plugin 612.v84da_9c54906d and earlier and in Pipeline: Deprecated Groovy Libraries Plugin 583.vf3b_454e43966 and earlier, the `library` step can be used to invoke sandbox-generated synthetic constructors in crafted untrusted libraries and construct any subclassable type. This is similar to SECURITY-582 in the [2017-08-07 security advisory](https://www.jenkins.io/security/advisory/2017-08-07/#multiple-groovy-language-features-allowed-script-security-plugin-sandbox-bypass), but in a different plugin.

This vulnerability allows attackers with permission to define untrusted Pipeline libraries and to define and run sandboxed Pipelines, to bypass the sandbox protection and execute arbitrary code in the context of the Jenkins controller JVM.

Pipeline: Groovy Libraries Plugin 613.v9c41a_160233f rejects improper calls to sandbox-generated synthetic constructors when using the `library` step.

Pipeline: Deprecated Groovy Libraries Plugin 588.v576c103a_ff86 no longer contains the `library` step. It has been moved into the Pipeline: Groovy Libraries Plugin.

Missing Authorization
Jenkins Blue Ocean Plugin 1.25.3 and earlier does not perform a permission check in several HTTP endpoints, allowing attackers with Overall/Read permission to connect to an attacker-specified HTTP server.

Arbitrary file read vulnerability in Jenkins Pipeline Utility Steps Plugin
Pipeline Utility Steps Plugin implements a `readProperties` Pipeline step that supports interpolation of variables using the Apache Commons Configuration library.

Pipeline Utility Steps Plugin 2.13.1 and earlier does not restrict the set of enabled prefix interpolators and bundles versions of this library that enable the `file:` prefix interpolator by default.

This allows attackers able to configure Pipelines to read arbitrary files from the Jenkins controller file system.

Pipeline Utility Steps Plugin 2.13.2 restricts the set of prefix interpolators enabled by default to `base64Decoder:`, `base64Encoder:`, `date:`, `urlDecoder:`, and `urlEncoder:`.

Administrators can set the [Java system property](https://www.jenkins.io/doc/book/managing/system-properties/) `org.jenkinsci.plugins.pipeline.utility.steps.conf.ReadPropertiesStepExecution.CUSTOM_PREFIX_INTERPOLATOR_LOOKUPS` to customize which prefix interpolators are enabled.

Stored XSS vulnerability in Jenkins Pipeline: Supporting APIs Plugin
Pipeline: Supporting APIs Plugin provides a feature to add hyperlinks, that send POST requests when clicked, to build logs. These links are used by Pipeline: Input Step Plugin to allow users to proceed or abort the build, or by Pipeline: Job Plugin to allow users to forcibly terminate the build after aborting it.

Pipeline: Supporting APIs Plugin 838.va_3a_087b_4055b and earlier does not sanitize or properly encode URLs of these hyperlinks in build logs.

This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to create Pipelines.

Pipeline: Supporting APIs Plugin 839.v35e2736cfd5c properly encodes URLs of these hyperlinks in build logs.

Whole-script approval in Jenkins Script Security Plugin vulnerable to SHA-1 collisions
Script Security Plugin 1189.vb_a_b_7c8fd5fde and earlier stores whole-script approvals as the [SHA-1 hash](https://en.wikipedia.org/wiki/SHA-1) of the approved script. SHA-1 no longer meets the security standards for producing a cryptographically secure message digest.

Script Security Plugin 1190.v65867a_a_47126 uses SHA-512 for new whole-script approvals. Previously approved scripts will have their SHA-1 based whole-script approval replaced with a corresponding SHA-512 whole-script approval when the script is next used.

Whole-script approval only stores the SHA-1 or SHA-512 hash, so it is not possible to migrate all previously approved scripts automatically on startup.

Administrators concerned about SHA-1 collision attacks on the whole-script approval feature are able to revoke all previous (SHA-1) script approvals on the In-Process Script Approval page.

Jenkins GitHub plugin uses weak webhook signature function
Jenkins GitHub Plugin 1.34.4 and earlier uses a non-constant time comparison function when checking whether the provided and computed webhook signatures are equal, allowing attackers to use statistical methods to obtain a valid webhook signature. GitHub Plugin 1.34.5 uses a constant-time comparison when validating the webhook signature.

CSRF protection for any URL can be bypassed in Jenkins Pipeline: Input Step Plugin
Pipeline: Input Step Plugin 451.vf1a_a_4f405289 and earlier does not restrict or sanitize the optionally specified ID of the `input` step. This ID is used for the URLs that process user interactions for the given `input` step (proceed or abort) and is not correctly encoded.

This allows attackers able to configure Pipelines to have Jenkins build URLs from `input` step IDs that would bypass the CSRF protection of any target URL in Jenkins when the `input` step is interacted with.

Pipeline: Input Step Plugin 456.vd8a_957db_5b_e9 limits the characters that can be used for the ID of `input` steps in Pipelines to alphanumeric characters and URL-safe punctuation. Pipelines with `input` steps having IDs with prohibited characters will fail with an error.

This includes Pipelines that have already been started but not finished before Jenkins is restarted to apply this update.

[Pipeline: Declarative Plugin](https://plugins.jenkins.io/pipeline-model-definition/) provides an `input` directive that is internally using the `input` step, and specifies a non-default ID if not user-defined. Pipeline: Declarative Plugin 2.2114.v2654ca_721309 and earlier may specify values incompatible with this new restriction on legal values: `input` directives in a `stage` use the stage name (which may include prohibited characters) and `input` directives in a `matrix` will use a value generated from the matrix axis values (which always includes prohibited characters). Administrators are advised to update Pipeline: Input Step Plugin and Pipeline: Declarative Plugin at the same time, ideally while no Pipelines are running.

Lack of authentication mechanism in Jenkins Git Plugin webhook
Git Plugin provides a webhook endpoint at `/git/notifyCommit` that can be used to notify Jenkins of changes to an SCM repository. For its most basic functionality, this endpoint receives a repository URL, and Jenkins will schedule polling for all jobs configured with the specified repository. In Git Plugin 4.11.3 and earlier, this endpoint can be accessed with GET requests and without authentication. In addition to this basic functionality, the endpoint also accept a `sha1` parameter specifying a commit ID. If this parameter is specified, jobs configured with the specified repo will be triggered immediately, and the build will check out the specified commit. Additionally, the output of the webhook endpoint will provide information about which jobs were triggered or scheduled for polling, including jobs the user has no permission to access. This allows attackers with knowledge of Git repository URLs to trigger builds of jobs using a specified Git repository and to cause them to check out an attacker-specified commit, and to obtain information about the existence of jobs configured with this Git repository. Git Plugin 4.11.4 requires a `token` parameter which will act as an authentication for the webhook endpoint. While GET requests remain allowed, attackers would need to be able to provide a webhook token. For more information see [the plugin documentation](https://github.com/jenkinsci/git-plugin/#push-notification-from-repository).

SnakeYaml Constructor Deserialization Remote Code Execution
### Summary
SnakeYaml's `Constructor` class, which inherits from `SafeConstructor`, allows
any type be deserialized given the following line:

new Yaml(new Constructor(TestDataClass.class)).load(yamlContent);

Types do not have to match the types of properties in the
target class. A `ConstructorException` is thrown, but only after a malicious
payload is deserialized.

### Severity
High, lack of type checks during deserialization allows remote code execution.

### Proof of Concept
Execute `bash run.sh`. The PoC uses Constructor to deserialize a payload
for RCE. RCE is demonstrated by using a payload which performs a http request to
http://127.0.0.1:8000.

Example output of successful run of proof of concept:

```
$ bash run.sh

[+] Downloading snakeyaml if needed
[+] Starting mock HTTP server on 127.0.0.1:8000 to demonstrate RCE
nc: no process found
[+] Compiling and running Proof of Concept, which a payload that sends a HTTP request to mock web server.
[+] An exception is expected.
Exception:
Cannot create property=payload for JavaBean=Main$TestDataClass@3cbbc1e0
 in 'string', line 1, column 1:
    payload: !!javax.script.ScriptEn ... 
    ^
Can not set java.lang.String field Main$TestDataClass.payload to javax.script.ScriptEngineManager
 in 'string', line 1, column 10:
    payload: !!javax.script.ScriptEngineManag ... 
             ^

	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:291)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:172)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:332)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:230)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:220)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:174)
	at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:158)
	at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:491)
	at org.yaml.snakeyaml.Yaml.load(Yaml.java:416)
	at Main.main(Main.java:37)
Caused by: java.lang.IllegalArgumentException: Can not set java.lang.String field Main$TestDataClass.payload to javax.script.ScriptEngineManager
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
	at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81)
	at java.base/java.lang.reflect.Field.set(Field.java:780)
	at org.yaml.snakeyaml.introspector.FieldProperty.set(FieldProperty.java:44)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:286)
	... 9 more
[+] Dumping Received HTTP Request. Will not be empty if PoC worked
GET /proof-of-concept HTTP/1.1
User-Agent: Java/11.0.14
Host: localhost:8000
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
Connection: keep-alive
```

### Further Analysis
Potential mitigations include, leveraging SnakeYaml's SafeConstructor while parsing untrusted content.

See https://bitbucket.org/snakeyaml/snakeyaml/issues/561/cve-2022-1471-vulnerability-in#comment-64581479 for discussion on the subject.

### Timeline
**Date reported**: 4/11/2022
**Date fixed**:  [30/12/2022](https://bitbucket.org/snakeyaml/snakeyaml/pull-requests/44)
**Date disclosed**: 10/13/2022