Many VMware Products Affected by SACK Linux Vulnerabilities

Over 30 VMware products are affected by SACK Panic and SACK Slowness, two recently disclosed Linux kernel vulnerabilities that can be exploited remotely without authentication for denial-of-service (DoS) attacks.

The security holes, discovered by a researcher working for Netflix, are related to how the kernel handles TCP Selective Acknowledgement (SACK) packets with a low minimum segment size (MSS). They could impact many devices, including servers, Android smartphones and embedded systems.

There are a total of three vulnerabilities tracked as SACK Panic (CVE-2019-11477), SACK Slowness (CVE-2019-11478, which also impacts FreeBSD), and CVE-2019-11479.

VMware has determined that SACK Panic and SACK Slowness impact many of its products. The company has assigned SACK Panic a severity rating of “important” with a CVSS score of 7.5, and SACK Slowness a severity rating of “moderate” with a CVSS score of 5.3.

“A malicious actor must have network access to an affected system including the ability to send traffic with low MSS values to the target. Successful exploitation of these issues may cause the target system to crash or significantly degrade performance,” VMware said in an advisory.

The vulnerabilities have been found to impact AppDefense, Container Service Extension, Enterprise PKS, Horizon, Hybrid Cloud Extension, Identity Manager, Integrated OpenStack, NSX, Pulse Console, SD-WAN, Skyline Collector, Unified Access Gateway, vCenter Server Appliance, vCloud, vRealize and vSphere products.

VMware is working on patches for each of the affected products, but so far it has only released updates for SD-WAN software, Unified Access Gateway, and vCenter Server Appliance.

The company noted that some VMware Virtual Appliances can be protected against potential attacks by disabling SACK or by configuring the firewall to drop connections with a low MSS. These recommendations apply to any system impacted by the vulnerabilities. VMware says specific workarounds are available for the vCloud Director for Service Providers Appliance.

Related: VMware Patches Vulnerabilities in Tools, Workstation

Related: VMware Patches Flaws Disclosed at Pwn2Own 2019

Related: VMware Patches DoS, Information Disclosure Flaws in Graphics Components

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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