CISCO addresses DoS bugs in CISCO ESA products [securityaffairs]

Cisco addressed two DoS vulnerabilities in CISCO ESA products that can be exploited by remote unauthenticated attacker.

Cisco fixed two denial-of-service (DoS) flaws in Email Security Appliance (ESA) products that can be exploited by a remote unauthenticated attacker.

The first flaw tracked as CVE-2018-15453  has been rated as “critical,” it is a memory corruption bug caused by improper input validation in emails signed with Secure/Multipurpose Internet Mail Extensions (S/MIME). The attacker could send a specially crafted S/MIME email to vulnerable ESA products and can cause appliances to reload and enter a DoS condition.

“A vulnerability in the Secure/Multipurpose Internet Mail Extensions (S/MIME) Decryption and Verification or S/MIME Public Key Harvesting features of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause an affected device to corrupt system memory.” reads the security advisory published by Cisco.

“A successful exploit could cause the filtering process to unexpectedly reload, resulting in a denial of service (DoS) condition on the device. “

Experts pointed out that the DoS condition is permanent because even after the software restart, it will process the same malicious email.

To restore the Cisco ESA product it is necessary to manually fix it.

“A successful exploit could allow the attacker to cause a permanent DoS condition. This vulnerability may require manual intervention to recover the ESA. ” continues the advisory.

“This vulnerability affects all software versions prior to the first fixed release of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA), both virtual and hardware appliances, if the software is configured for S/MIME Decryption and Verification or S/MIME Public Key Harvesting.”

The second DoS flaw in Cisco ESA, tracked as CVE-2018-15460 and rated “high severity,” affects the message filtering feature of AsyncOS software.

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