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This Week in Security: Hornet, Gogs, and Blinkenlights
Microsoft has published a patch-set for the Linux kernel, proposing the Hornet Linux Security Module (LSM). If you haven’t been keeping up with the kernel contributor scoreboard, Microsoft is #11 at time of writing and that might surprise you. The reality is that Microsoft’s biggest source of revenue is their cloud offering, and Azure is over half Linux, so Microsoft really is incentivized to make Linux better.
The Hornet LSM is all about more secure eBPF programs, which requires another aside: What is eBPF? First implemented in the Berkeley Packet Filter, it’s a virtual machine in the kernel, that allows executing programs in kernel space. It was quickly realized that this ability to run a script in kernel space was useful for far more than just filtering packets, and the extended Berkeley Packet Filter was born. eBPF is now used for load balancing, system auditing, security and intrusion detection, and lots more.
This unique ability to load scripts from user space into kernel space has made eBPF useful for malware and spyware applications, too. There is already a signature scheme to restrict eBPF programs, but Hornet allows for stricter checks and auditing. The patch is considered a Request For Comments (RFC), and points out that this existing protection may be subject to Time Of Check / Time Of Use (TOCTOU) attacks. It remains to be seen whether Hornet passes muster and lands in the upstream kernel.
Patch Tuesday
Linux obviously isn’t the only ongoing concern for Microsoft, and it’s the time of month to talk about patch Tuesday. There are 57 fixes that are considered vulnerabilities, and additional changes that are just classified internally as bug fixes. There were three of those vulnerabilities that were publicly known before the fix, and one of those was known to be actively used in attacks in the wild.
CVE-2025-62221 was an escalation of privilege flaw in the Windows Cloud Files Mini Filter Driver. In Windows, a minifilter is a kernel driver that attach to the file system software, to monitor or modify file operations. This flaw was a use-after-free that allowed a lesser-privileged attacker to gain SYSTEM privileges.
Gogs
Researchers at Wiz found an active exploitation campaign that uses CVE-2025-8110, a previously unknown vulnerability in Gogs. The GO Git Service, hence the name, is a self-hosted GitHub/GitLab alternative written in Go. It’s reasonably popular, with 1,400 of them exposed to the Internet.
The vulnerability was a bypass of CVE-2024-55947, a path traversal vulnerability that allowed a malicious user to upload files to arbitrary locations. That was fixed with Gogs 0.13.1, but the fix failed to account for symbolic links (symlinks). Namely, as far as the git protocol is concerned, symlinks are completely legal. The path traversal checking doesn’t check for symlinks during normal git access, so a symlink pointing outside the repository can easily be created. And then the HTTPS file API can be used to upload a file to that symlink, again allowing for arbitrary writes.
The active exploitation on this vulnerability is particularly widespread. Of the 1400 Gogs instances on the Internet, over 700 show signs of compromise, in the form of new repositories with randomized names. It’s possible that even more instances have been compromised, and the signs have been covered. The attack added a symlink to .git/config, and then overwriting that file with a new config that defines the sshCommand setting. After exploitation, a Supershell malware was installed, establishing ongoing remote control.
The most troubling element of this story is that the vulnerability was first discovered in the wild back in July and was reported to the Gogs project at that time. As of December 11, the vulnerability has not been fixed or acknowledged. After five months of exploitation without a patch, it seems time to acknowledge that Gogs is effectively unmaintained. There are a couple of active forks that don’t seem to be vulnerable to this attack; time to migrate.
Blinkenlights
There’s an old story I always considered apocryphal, that data could be extracted from the blinking lights of network equipment, leading to a few ISPs to boast that they covered all their LEDs with tape for security. While there may have been a bit of truth to that idea, it definitely served as inspiration for [Damien Cauquil] at Quarkslab, reverse engineering a very cheap smart watch.
The watches were €11.99 last Christmas, and a price point that cheap tickles the curiosity of nearly any hacker. What’s on the inside? What does the firmware look like? The micro-controller was by the JieLi brand, and it’s a bit obscure, with no good way to pull the firmware back off. With no leads there, [Damien] turned to the Android app and the Bluetooth Low Energy connection. One of the functions of the app is uploading custom watch dials. Which of course had to be tested by creating a custom watch face featuring a certain Rick Astley.
But those custom watch faces have a quirk. The format internally uses byte offsets, and the watch doesn’t check for that offset to be out of bounds. A ridiculous scheme was concocted to abuse this memory leak to push firmware bytes out as pixel data. It took a Raspberry Pi Pico sniffing the SPI bus to actually recover those bytes, but it worked! Quite the epic hack.
Bits and Bytes
Libpng has an out of bounds read vulnerability, that was just fixed in 1.6.52. What’s weird about this one is that the vulnerability is can be triggered by completely legitimate PNG images. The good news is that is vulnerability only effects the simplified API, so not every user of libpng is in the blast radius.
And finally, Google has pushed out an out-of-band update to Chrome, fixing a vulnerability that is being exploited in the wild. The Hacker News managed to connect the bug ID to a pull request in the LibANGLE library, a translation layer between OpenGL US calls into Direct3D, Vulkan, and Metal. The details there suggests the flaw is limited to the macOS platform, as the fix is in the metal renderer. Regardless, time to update!
