The Patching Friars' AlmanacA calendar of CVE saints

November 8

ThrangrycatHoly card for thrangrycat, generated with AI (Claude, Anthropic) for the Lunario dei Frati Patchatori.CC BY-NC-SA 4.0 Thrangrycat FELIS IRATA REGNAT
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Saint Thrangrycat, the Angry Cat of Secure Boot

Patron of Cisco routers, Secure Boot FPGAs, and domain names made of angry faces.

Life

On 8 November 2018 Red Balloon Security presented Thrangrycat, a flaw in the hardware Secure Boot of many Cisco devices: an attacker already holding admin rights could rewrite the FPGA that guards secure boot and, bypassing its checks, boot malicious firmware that not even a reinstall removes. The name is three angry cats, and the research's official site really lived at an address made of furious-cat emoji (CVE-2019-1649).

Prayer

O Saint Thrangrycat, furious cat who rewrites the guardian of boot, let our roots of trust not be rewritten. Amen.

How to celebrate

Celebrated by updating Cisco firmware and limiting who holds admin access, with a cat nearby for luck.

Rewrite the guardian and you command the fortress.

Technical record

Disclosed on
November 8 2018
CVE
CVE-2019-1649CVE-2019-1862
CVSS
7.2
Product
Cisco · Cisco Routers

A vulnerability in the logic that handles access control to one of the hardware components in Cisco's proprietary Secure Boot implementation could allow an authenticated, local attacker to write a modified firmware image to the component. This vulnerability affects multiple Cisco products that support hardware-based Secure Boot functionality. The vulnerability is due to an improper check on the area of code that manages on-premise updates to a Field Programmable Gate Array (FPGA) part of the Secure Boot hardware implementation. An attacker with elevated privileges and access to the underlying operating system that is running on the affected device could exploit this vulnerability by writing a modified firmware image to the FPGA. A successful exploit could either cause the device to become unusable (and require a hardware replacement) or allow tampering with the Secure Boot verification process, which under some circumstances may allow the attacker to install and boot a malicious software image. An attacker will need to fulfill all the following conditions to attempt to exploit this vulnerability: Have privileged administrative access to the device. Be able to access the underlying operating system running on the device; this can be achieved either by using a supported, documented mechanism or by exploiting another vulnerability that would provide an attacker with such access. Develop or have access to a platform-specific exploit. An attacker attempting to exploit this vulnerability across multiple affected platforms would need to research each one of those platforms and then develop a platform-specific exploit. Although the research process could be reused across different platforms, an exploit developed for a given hardware platform is unlikely to work on a different hardware platform.

Sources: xn--538haa.fm

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