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AUSCERT External Security Bulletin Redistribution
Cisco Web Security Appliance Malformed HTTP Response Denial
of Service Vulnerability
10 September 2015
AusCERT Security Bulletin Summary
Product: Cisco Web Security Appliance
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote with User Interaction
CVE Names: CVE-2015-6290
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Cisco Web Security Appliance Malformed HTTP Response Denial of Service
Threat Type: CWE-119: Buffer Errors
IntelliShield ID: 40896
First Published: 2015 September 09 20:07 GMT
Last Published: 2015 September 09 20:07 GMT
Port: Not available
Urgency: Unlikely Use
Severity: Mild Damage
CVSS Base: 4.3
CVSS Temporal: 3.7
Version Summary: Cisco Web Security Appliance contains a vulnerability
that could allow an unauthenticated, remote attacker to cause a denial of
service condition. Updates are not available.
A vulnerability in the web interface of the Cisco Web Security Appliance
(WSA) could allow an unauthenticated, remote attacker to cause a partial
denial of service (DoS) condition due to memory management failures during
processing of TCP connections.
The vulnerability is due to the improper handling of a malformed HTTP server
responses. An unauthenticated, remote attacker with a privileged network
position could exploit the vulnerability by conducting a man-in-the-middle
(MitM) attack and supplying malformed HTTP server responses to the vulnerable
device. A successful exploit could allow the attacker to cause the device
to improperly close TCP connections and fail to free memory resources,
resulting in a partial DoS condition.
Cisco has confirmed the vulnerability; however, software updates are
At the time this alert was first published, Cisco Web Security Appliance
version 8.0.7 was affected. Later versions of Cisco WSA may also be affected.
To exploit the vulnerability, the attacker would need to send crafted HTTP
requests to the targeted system through the WSA web interface. Because the
attacker does not need to authenticate to send the crafted HTTP requests,
the likelihood of an exploit is increased.
Cisco has released bug ID CSCuw10426 for registered users that contains
additional details and an up-to-date list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to
cause a DoS condition on the targeted device.
The vulnerability is due to improper handling of malformed HTTP server
An attacker could exploit this vulnerability by causing the vulnerable
application to process a malformed HTTP server response. A successful
exploit could allow the attacker to cause a DoS condition on the targeted
device due to improperly freed memory resources.
Administrators may consider using IP-based access control lists (ACLs)
to allow only trusted systems to access the affected systems.
Administrators are advised to implement physical security for production
Administrators are advised to contact the vendor regarding future updates
Updates are not available.
The security vulnerability applies to the following combinations of products.
Cisco Cisco Web Security Appliance (WSA) 8.0 Base, .5, .5 Hot Patch
1, .6, .7
The urgency and severity ratings of this alert are not tailored to
individual users; users may value alerts differently based upon their
network configurations and circumstances. THE ALERT, AND INFORMATION
CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION
CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN
RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON
OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT
NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
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