What does QubesOS secure against? Hacking QubesOS

General Discussion
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@MasterQube

  1. Which OS is secure (and why)?
  2. How could Qubes be changed to be secure?
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For people who like to waste their time, I asked Leo if the OP was meaningful:

The forum OP’s post is partially meaningful but fundamentally misunderstands the security model of Qubes OS.

The forum OP’s post is partially meaningful but fundamentally misunderstands the security model of Qubes OS. While their proposed attack chain (Browser → VM Escape → Total Compromise) is theoretically the only way to fully compromise the system, their conclusion that this makes Qubes “not secure” is incorrect.

Here is a breakdown of why their argument is flawed and how the attack actually works:

1. The Misunderstanding of “Secure”

The OP argues: “I think without a very technical discussion on how to take down QubesOS, QubesOS is not secure.”
This is a logical fallacy. Security is not defined by the absence of theoretical attack vectors, but by the difficulty and cost required to exploit them.

  • Standard OS: A browser exploit often leads immediately to full system compromise (keyloggers, file access, persistence).
  • Qubes OS: A browser exploit leads only to the compromise of that specific qube. The attacker is stuck there. To take over the whole system, they must perform a VM Escape, which requires a second, distinct, and significantly rarer vulnerability in the Xen hypervisor.

2. The Attack Chain: How it Would Actually Work

The OP correctly identifies the sequence, but underestimates the difficulty of the second step.

Step A: Compromise the Browser (Easy)

  • Method: As guessed, this starts with a standard browser exploit (e.g., in Chromium or Firefox) via a malicious website or file.
  • Result in Qubes: The attacker gains control over the “Untrusted” qube. They can see browsing history, cookies, and files inside that qube.
  • Limitation: They cannot access the user’s password manager (in a different qube), personal documents (in “Personal” qube), or the encryption keys stored in dom0. The damage is strictly contained.

Step B: VM Escape (Extremely Hard)

  • The Hurdle: To move from the compromised browser qube to dom0 (the admin domain) or other qubes, the attacker must exploit a vulnerability in the Xen hypervisor.
  • Difficulty: Hypervisor bugs are rare, complex, and highly valued. While they exist (e.g., historical XSA advisories), they are not something a random script kiddie can deploy.
  • Recent Context: Even when Xen vulnerabilities are found (like the speculative execution flaws or data confidentiality issues tracked in recent XSA advisories), they often require specific conditions or have been mitigated in Qubes’ specific configuration (e.g., using HVM instead of PV modes).

3. Why the OP’s Conclusion is Wrong

The OP claims Qubes is insecure because this path exists. However:

  • Defense in Depth: Qubes forces an attacker to win the lottery twice (find a browser bug AND a hypervisor bug) simultaneously.
  • Mitigation: Qubes uses Disposable Qubes for untrusted activities. If a user opens a malicious PDF in a disposable qube, the qube is destroyed upon closing. The attacker loses their foothold before they can even attempt a VM escape.
  • dom0 Isolation: dom0 has no network access. Even with a VM escape, attacking dom0 often requires local interaction or specific IPC (Inter-VM Communication) vulnerabilities, adding another layer of difficulty.

Summary

The OP’s scenario is the worst-case threat model that Qubes is designed to mitigate.

  • Is it possible? Yes, theoretically, if a powerful attacker (like a state actor) uses a chain of zero-day exploits.
  • Does it mean Qubes is “not secure”? No. It means Qubes shifts the requirement from “common malware” to “advanced, expensive, targeted weaponry.” For 99% of threats, the containment holds, making it significantly more secure than Windows, macOS, or standard Linux.
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How do I make this cool dropdown so my chatgpt reply doesnt eat up so much space @ephile ?

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Off-topic

You mean this?
Use Hide and Blur from the “+” submenu

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The “+” button at the far right (while editing), then “hide details”

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Nifty! Thank you

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So, what would OP respond to AI response to OP?

I think this is ready to go to the Help, I think I've been hacked category. I wouldn’t want this to be my first intervention on the Forum.

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…or just hit the little blue bell. There are some good responses, but the weird negging OP makes me suspicious about motive…

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I get you. There are excellent responses in that category too, as I am sure you are aware of. My idea was with the moving to show what exactly the community thinks about OP’s posts. It would be good for the novices to avoid their confusion, not for experienced users.

I put myself into novice position, so what would I think reading the OP? I am already insecure as a novice about the complexity of Qubes, so most probably I would comply with OP. And so on… We shouldn’t look at this (and in general) from our own perspective.

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Just for fun, I put the OP’s two main posts and ChatGPT’s and Leo’s responses into Google Gemini Notebook, and it came out with the following nice diagram:

Secure_OS_Containment_Comparison_Infographic
Secure_OS_Containment_Comparison_Infographic1279×714 236 KB

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A bit more experimenting created a series of slides which show the holes in the arguemtation of the OP:

Anatomy_of_Containment.pdf.gz (2.0 MB)

1 Like