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Forwarding Loop Attacks in Content Delivery Networks may result in denial of service

Vulnerability Note VU#938151

Original Release Date: 2016-02-29 | Last Revised: 2016-03-04

Overview

Content Delivery Networks (CDNs) may in some scenarios be manipulated into a forwarding loop, which consumes server resources and causes a denial of service (DoS) on the network.

Description

CWE-400: Uncontrolled Resource Consumption ('Resource Exhaustion')

Content Delivery Networks (CDNs) are used to improve website performance and scalability by connecting a user to geographically nearby server for content. CDNs typically operate in two modes, a "push" mode allowing a user to upload content to the CDN for later distribution, or a "pull" mode which effectively acts as a reverse proxy.

In some scenarios, a malicious user can manipulate "pull mode" forwarding to forward in an internal loop within the CDN. This effectively launches a denial of service (DoS) attack against the CDN by consuming large amounts of resources.

More information is provided in the researcher's conference paper.

Impact

A remote attacker may be able to create a denial of service condition in CDNs, preventing access to hosted content.

Solution

The researchers and CERT have reached out to known affected CDNs to inform them of this attack. CDNs are implementing their own counter-measures to this attack. If you are an employee of a CDN, the CERT/CC encourages you to review the researcher's conference paper to determine if your CDN may be impacted.

Vendor Information

938151
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Akamai Technologies, Inc.

Updated:  March 04, 2016

Statement Date:   March 04, 2016

Status

  Affected

Vendor Statement

"Akamai is aware of the research paper titled "Forwarding-Loop Attacks in
Content Delivery Networks
<https://community.akamai.com/external-link.jspa?url=https%3A%2F%2Fwww.inter
netsociety.org%2Fsites%2Fdefault%2Ffiles%2Fblogs-media%2Fforwarding-loop-att
acks-content-delivery-networks.pdf> " published by Jianjun Chen et. al on
Feb. 29.  We have reviewed the researchers' findings, and are confident that
we already have adequate counter-measures in place to thwart any attempt to
use Akamai as an attack vector in the manner described by the paper.

The paper describes four types of forwarding-loop attacks against CDNs:
self-loop, intra-CDN loop, inter-CDN loop and dam flooding. The paper
acknowledges that Akamai is not vulnerable to the first two. The third
attack (the "inter-CDN loop attack") is described as a looping between
multiple CDNs.  Finally, the fourth -- "dam flooding" -- is described as
coupling "forwarding-loop attacks with timely controlled HTTP responses to
significantly increase damage."

While Akamai does not publicly disclose or discuss our security
countermeasures, we would like to reiterate that we have sufficient
countermeasures in place to detect and defend against all these attacks, as
well as substantial capacity to absorb traffic spikes. If you have any
additional questions/concerns, please reach out to your Akamai
representative."

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

https://blogs.akamai.com/2016/03/akamai-response-to-forwarding-loop-issue.html https://community.akamai.com/community/security-research-and-intelligence/blog/2016/03/03/akamai-response-to-forwarding-loop-issue

Addendum

There are no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

CDNsun

Notified:  December 27, 2015 Updated:  January 04, 2016

Statement Date:   December 30, 2015

Status

  Affected

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Addendum

There are no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

OnApp

Updated:  February 29, 2016

Statement Date:   January 12, 2016

Status

  Affected

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Addendum

There are no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.


CVSS Metrics

Group Score Vector
Base 7.1 AV:N/AC:M/Au:N/C:N/I:N/A:C
Temporal 6.1 E:POC/RL:U/RC:UR
Environmental 4.6 CDP:ND/TD:M/CR:ND/IR:ND/AR:ND

References

Credit

Thanks to Jianjun Chen and Jian Jiang for reporting this vulnerability.

This document was written by Garret Wassermann.

Other Information

CVE IDs: None
Date Public: 2016-02-24
Date First Published: 2016-02-29
Date Last Updated: 2016-03-04 19:35 UTC
Document Revision: 32

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