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AUSCERT External Security Bulletin Redistribution
ESB-2015.2550
Cisco Email Security Appliance Max Files Denial of Service Vulnerability
6 October 2015
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AusCERT Security Bulletin Summary
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Product: Cisco Email Security Appliance
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Existing Account
Resolution: Mitigation
CVE Names: CVE-2015-6309
Original Bulletin:
http://tools.cisco.com/security/center/mviewAlert.x?alertId=41241
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Vulnerability Alert
Cisco Email Security Appliance Max Files Denial of Service Vulnerability
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 41241 Version: 1
First Published: 2015 September 30 18:56 GMT Last Published: 2015 September 30
18:56 GMT
Vector: Low
Authentication: Single
Exploit: Functional
CVE: CVE-2015-6309
Urgency: 2
Credibility: 5
Severity: 3
CVSS Base: 6.8
CVSS Temporal: 6.5
Version Summary:
Cisco Email Security Appliance contains a vulnerability that could allow an
authenticated, remote attacker to cause a denial of service condition. Updates
are not available.
Aliases/Variants None Virus Name: None Description:
A vulnerability in file descriptor handling of the Cisco Email Security
Appliance (ESA) could allow an authenticated, remote attacker to cause a
denial of service (DoS) condition due to the affected device unexpectedly
reloading.
The vulnerability is due to failure to release file descriptors when the
requested file action is completed. An attacker could exploit this
vulnerability by sending a crafted HTTP request to the affected device. A
successful exploit could allow the attacker to cause a DoS condition due to
the affected device failing to release file descriptors. When all file
descriptors are in use, the device can reload unexpectedly.
Cisco has confirmed the vulnerability; however, software updates are not
available.
Impact
An authenticated, remote attacker could exploit this vulnerability to
cause an affected device to reload unexpectedly, resulting in a DoS condition.
Warning Indicators
At the time this alert was first published, Cisco ESA releases 8.5.6-106
and 9.6.0-042 were vulnerable. Later releases of Cisco ESA may also be
vulnerable.
Technical Information
The vulnerability is due to improper handling of file descriptors after
the completion of a requested file action by an affected device.
An authenticated, remote attacker could exploit this vulnerability by
sending a crafted HTTP request to the affected device. A successful exploit
could cause the affected device to fail to release file descriptors, which
could cause the device to unexpectedly reload, resulting in a DoS condition.
Vendor Announcements
Cisco has released bug ID CSCuw32211 for registered users, which contains
additional details and an up-to-date list of affected product versions.
IntelliShield Analysis
To exploit this vulnerability, an attacker must authenticate to the
targeted device. This access requirement reduces the likelihood of a
successful exploit.
Cisco indicates through the CVSS score that functional exploit code
exists; however, the code is not known to be publicly available.
Safeguards
Administrators are advised to contact the vendor regarding future updates
and releases.
Administrators are advised to allow only trusted users to have network
access.
Administrators are advised to allow only privileged users to access
administration or management systems.
Administrators are advised to monitor affected systems.
Patches/Software
Software updates are not available.
Primary Product Set (1)
LEGAL DISCLAIMER
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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