# CVE-2026-45878: drm/amdkfd: Fix watch_id bounds checking in debug address watch v2

> A local attacker can trigger a buffer overflow in the AMD GPU driver by passing a large watch_id, potentially leading to code execution or privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 27 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-45878, DEBIAN-CVE-2026-45878, GHSA-4753-mhw2-5g7r, ROOT-OS-UBUNTU-2404-CVE-2026-45878, UBUNTU-CVE-2026-45878

## What is CVE-2026-45878?

CVE-2026-45878 is a high-severity vulnerability in Linux kernel, published on 27 May 2026. 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:

drm/amdkfd: Fix watch_id bounds checking in debug address watch v2

The address watch clear code receives watch_id as an unsigned value
(u32), but some helper functions were using a signed int and checked
bits by shifting with watch_id.

If a very large watch_id is passed from userspace, it can be converted
to a negative value.  This can cause invalid shifts and may access
memory outside the watch_points array.

drm/amdkfd: Fix watch_id bounds checking in debug address watch v2

Fix this by checking that watch_id is within MAX_WATCH_ADDRESSES before
using it.  Also use BIT(watch_id) to test and clear bits safely.

This keeps the behavior unchanged for valid watch IDs and avoids
undefined behavior for invalid ones.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_debug.c:448
kfd_dbg_trap_clear_dev_address_watch() error: buffer overflow
'pdd->watch_points' 4 <= u32max user_rl='0-3,2147483648-u32max' uncapped

drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_debug.c
    433 int kfd_dbg_trap_clear_dev_address_watch(struct kfd_process_device *pdd,
    434                                         uint32_t watch_id)
    435 {
    436         int r;
    437
    438         if (!kfd_dbg_owns_dev_watch_id(pdd, watch_id))

kfd_dbg_owns_dev_watch_id() doesn't check for negative values so if
watch_id is larger than INT_MAX it leads to a buffer overflow.
(Negative shifts are undefined).

    439                 return -EINVAL;
    440
    441         if (!pdd->dev->kfd->shared_resources.enable_mes) {
    442                 r = debug_lock_and_unmap(pdd->dev->dqm);
    443                 if (r)
    444                         return r;
    445         }
    446
    447         amdgpu_gfx_off_ctrl(pdd->dev->adev, false);
--> 448         pdd->watch_points[watch_id] = pdd->dev->kfd2kgd->clear_address_watch(
    449                                                         pdd->dev->adev,
    450                                                         watch_id);

v2: (as per, Jonathan Kim)
 - Add early watch_id >= MAX_WATCH_ADDRESSES validation in the set path to
   match the clear path.
 - Drop the redundant bounds check in kfd_dbg_owns_dev_watch_id().

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-45878?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45878?

Apply the vendor's patch.

## Is CVE-2026-45878 being exploited?

There is no known exploitation of CVE-2026-45878 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45878 and fix it if it is affected.

What it is: CVE-2026-45878 is a high-severity vulnerability in Linux kernel, published on 27 May 2026. 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-2026-45878 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-45878/ (Markdown: https://insights.sbomify.com/CVE-2026-45878/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45878
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45878
- OSV: https://osv.dev/vulnerability/CVE-2026-45878

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45878/
Summaries are generated and may contain mistakes; the official description above is the record.