Hack The Box Cobblestone Stats (Insane Linux)
HTB Cobblestone: retired insane Linux box, 3.4/5 from 211 reviews, 2,713 user owns. Final stats, difficulty read and prep. Spoiler-free, no flags.
Cobblestone was an active Hack The Box machine, an insane Linux box by c1sc0, released 2025-08-09 in Season 8, worth 50 points and 1,365 XP. It retired in August 2026 after just over a year live, the longest run of any machine on the board, so what follows is its final data and an honest read of the difficulty. No chain, no flags, no spoilers.
HTB Cobblestone at a glance
| Machine ID | 691 |
| Difficulty | Insane (50 pts / 1,365 XP) |
| OS | Linux |
| Released | 2025-08-09 (Season 8) |
| Status | retired August 2026, after a year live |
| Maker | c1sc0 |
| Rating | 3.4 / 5 from 211 reviews |
| User owns | 2,713 |
| Root owns | 2,575 |
| User → root drop | 5.1% |
| User blood | 1h 12m 57s by jaxafed |
| Root blood | 2h 15m 51s by Vz0n |
Community difficulty votes:
| Bucket | Votes | Share |
|---|---|---|
| Hard | 576 | 22.0% |
| Too Hard | 357 | 13.6% |
| Medium | 330 | 12.6% |
| Bit Hard | 319 | 12.2% |
| Brain Fuck | 247 | 9.4% |
Total votes: 2,621.
Is HTB Cobblestone hard?
Cobblestone was the oldest machine on the active list, released 9 August 2025 and live for just over a year. It retired in August 2026 rated 3.4 from 211 reviews, the lowest score of any Insane on the board and second-lowest overall, above only Connected.
The votes suggest why. For an Insane, the distribution is oddly flat and centered low: 576 Hard, 357 Too Hard, 330 Medium, 319 Bit Hard, and 247 Brainfuck out of 2,621. Barely a tenth of players thought it earned the Insane label, and a similar share thought it was Medium. Flat histograms like that usually mean the difficulty comes from something other than technical depth.
The pacing supports that: bloods at 1h12m (jaxafed) and 2h15m (Vz0n) are quick for Insane, and the user-to-root drop is only 5.1% across 2,713 user owns.
Take it for the 1,365 XP and the Linux practice, and go in expecting to spend your time on enumeration breadth rather than on a single hard technique. Read the rating as a warning about the experience rather than about your ability.
What to have ready for Cobblestone
- Budget days, not hours, and keep a running notes file. Insane Linux boxes are lost to a credential you found on day one and forgot by day three.
- Full TCP plus UDP, then re-scan after every pivot. The internal surface is where the real box lives; the external one is just the door.
- Expect custom code. Pull the application source, read it properly, and look for logic and trust flaws rather than CVE-shaped holes.
- Have
ligolo-ngorchiselworking end to end before you start, and assume more than one hop between you and root. - Container escapes, writable systemd units, capabilities, and inter-service trust are the recurring joints. Enumerate as every user and every service account you land on.
When the Cobblestone writeup lands
We publish full chains after a box retires, never while it’s active, and we don’t hand them to anyone outside the team. Cobblestone has retired, so the chain is clear to publish and the writeup lands in the same format as the HTB Manage one.
If you’d rather not wait, the team’s internal notes go out in our Discord first. That’s also where people work through the active board together, which is the part you’re actually allowed to do while a box is still live.
Related writeups
Retired Linux boxes we’ve already published: