let’s encrypt

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This Week In Security: Medical Backdoors, Strings, And Changes At Let’s Encrypt

February 7, 2025 by 12 Comments

There are some interesting questions afoot, with the news that the Contec CMS8000 medical monitoring system has a backdoor. And this isn’t the normal debug port accidentally left in the firmware. The CISA PDF has all the details, and it’s weird. The device firmware attempts to mount an NFS share from an IP address owned by an undisclosed university. If that mount command succeeds, binary files would be copied to the local filesystem and executed.

Additionally, the firmware sends patient and sensor data to this same hard-coded IP address. This backdoor also includes a system call to enable the eth0 network before attempting to access the hardcoded IP address, meaning that simply disabling the Ethernet connection in the device options is not sufficient to prevent the backdoor from triggering. This is a stark reminder that in the firmware world, workarounds and mitigations are often inadequate. For instance, you could set the gateway address to a bogus value, but a slightly more sophisticated firmware could trivially enable a bridge or alias approach, completely bypassing those settings. There is no fix at this time, and the guidance is pretty straightforward — unplug the affected devices.

Continue reading “This Week In Security: Medical Backdoors, Strings, And Changes At Let’s Encrypt” →

Let’s Encrypt Will Stop Working For Older Android Devices

December 1, 2020 by 20 Comments

Let’s Encrypt was founded in 2012, going public in 2014, with the aim to improve security on the web. The goal was to be achieved by providing free, automated access to SSL and TLS certificates that would allow websites to make the switch over to HTTPS without having to spend any money.

Hundreds of millions of sites rely on Let’s Encrypt for their HTTPS certificate needs. HTTPS security helps protect sites and users, and makes it harder for malicious actors to steal private information.

The project has just announced that, come September 1, 2021, some older software will stop trusting their certificates. Let’s look at why this has come to pass, and what it means going forward.

Certificates Expire

When Let’s Encrypt first went public in early 2016, they issued their own root certificate, by the name ISRG Root X1. However, it takes time for companies to include updated root certificates in their software, so until recently, all Let’s Encrypt certificates were cross-signed by an IdenTrust certificate, DST Root X3. This certificate had been around much longer, and was already supported by the vast majority of OSes and browsers in regular use. This allowed Let’s Encrypt to hit the ground running while they waited for the majority of software to support their own root certificate. Continue reading “Let’s Encrypt Will Stop Working For Older Android Devices” →