A vulnerability in the Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the configured user filters on an affected device. The vulnerability exists because the affected software insufficiently validates certain incoming SPF messages. An attacker could exploit this vulnerability by sending a custom SPF packet to an affected device. A successful exploit could allow the attacker to bypass the configured header filters, which could allow malicious content to pass through the device. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191002-esa-bypass
A vulnerability in the Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the configured user filters on an affected device.
The vulnerability exists because the affected software insufficiently validates certain incoming SPF messages. An attacker could exploit this vulnerability by sending a custom SPF packet to an affected device. A successful exploit could allow the attacker to bypass the configured header filters, which could allow malicious content to pass through the device.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191002-esa-bypass
At the time of publication, this vulnerability affected Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) releases earlier than Release 12.5.1
See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
There are no workarounds that address this vulnerability.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
At the time of publication, Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) releases 12.5.1 and later contained the fix for this vulnerability.
See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
Cisco would like to thank Fabian Henneke of the University of Bonn for reporting this vulnerability.
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.1 | Updated first fixed release number. | Vulnerable Products and Fixed Software | Final | 2020-February-18 |
| 1.0 | Initial public release. | - | Final | 2019-October-02 |
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