# CVE-2025-40155: iommu/vt-d: debugfs: Fix legacy mode page table dump logic

> A local attacker with debugfs access can trigger a kernel crash by reading IOMMU page tables in legacy mode due to uninitialized pointer usage.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Nov 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40155, DEBIAN-CVE-2025-40155, GHSA-x5w6-9frm-w2cc, ROOT-OS-DEBIAN-13-CVE-2025-40155, ROOT-OS-UBUNTU-2404-CVE-2025-40155, UBUNTU-CVE-2025-40155

## What is CVE-2025-40155?

CVE-2025-40155 is a high-severity vulnerability in Linux, published on 12 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: debugfs: Fix legacy mode page table dump logic

In legacy mode, SSPTPTR is ignored if TT is not 00b or 01b. SSPTPTR
maybe uninitialized or zero in that case and may cause oops like:

 Oops: general protection fault, probably for non-canonical address
       0xf00087d3f000f000: 0000 [#1] SMP NOPTI
 CPU: 2 UID: 0 PID: 786 Comm: cat Not tainted 6.16.0 #191 PREEMPT(voluntary)
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-5.fc42 04/01/2014
 RIP: 0010:pgtable_walk_level+0x98/0x150
 RSP: 0018:ffffc90000f279c0 EFLAGS: 00010206
 RAX: 0000000040000000 RBX: ffffc90000f27ab0 RCX: 000000000000001e
 RDX: 0000000000000003 RSI: f00087d3f000f000 RDI: f00087d3f0010000
 RBP: ffffc90000f27a00 R08: ffffc90000f27a98 R09: 0000000000000002
 R10: 0000000000000000 R11: 0000000000000000 R12: f00087d3f000f000
 R13: 0000000000000000 R14: 0000000040000000 R15: ffffc90000f27a98
 FS:  0000764566dcb740(0000) GS:ffff8881f812c000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000764566d44000 CR3: 0000000109d81003 CR4: 0000000000772ef0
 PKRU: 55555554
 Call Trace:
  <TASK>
  pgtable_walk_level+0x88/0x150
  domain_translation_struct_show.isra.0+0x2d9/0x300
  dev_domain_translation_struct_show+0x20/0x40
  seq_read_iter+0x12d/0x490
...

Avoid walking the page table if TT is not 00b or 01b.

## Which versions are affected by CVE-2025-40155?


## How do I fix CVE-2025-40155?

Apply the vendor's patch.

## Is CVE-2025-40155 being exploited?

There is no known exploitation of CVE-2025-40155 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40155 and fix it if it is affected.

What it is: CVE-2025-40155 is a high-severity vulnerability in Linux, published on 12 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40155 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-40155/ (Markdown: https://insights.sbomify.com/CVE-2025-40155/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40155
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40155
- OSV: https://osv.dev/vulnerability/CVE-2025-40155

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40155/
Summaries are generated and may contain mistakes; the official description above is the record.