A recently discovered flaw in Cisco IOS XE software with the HTTP Server feature enabled could allow a user with stolen credentials to execute code on a Cisco networking device with root privileges — a significant privilege escalation attack. Dubbed Thrangrycat by the researchers at Red Balloon Security who discovered the linked pair of vulnerabilities, these flaws, designated CVE-2019-1862, would allow an attacker to first bypass the Cisco Trust Anchor module (TAm), then conduct a remote code injection with root execution.
In the first exploit, an attacker would manipulate the bitstream responsible for defining the Field-Programmable Gate Array (FPGA) that holds the code for TAm — code that executes from the FPGA hardware at boot and is designed to insulate the device from boot-time exploits. In addition to bypassing secure boot, the attack code locks all future software updates out of the TAm.
Once the TAm is compromised, the attacker can log into the device and execute code at root privilege. Cisco has released a firmware update that patches the vulnerability, and acknowledges that there are no operational work-arounds to Thrangrycat.
The company plans to present details of the vulnerability and exploit at Black Hat USA 2019 in Las Vegas.
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