# CVE-2025-38055: perf/x86/intel: Fix segfault with PEBS-via-PT with sample_freq

> A local attacker can trigger a kernel segfault and denial of service by using PEBS-via-PT with sample frequency in the Linux kernel.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 18 Jun 2025
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2025-38055, DEBIAN-CVE-2025-38055, GHSA-hwwv-phfq-243p, ROOT-OS-UBUNTU-2404-CVE-2025-38055, UBUNTU-CVE-2025-38055

## What is CVE-2025-38055?

CVE-2025-38055 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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:

perf/x86/intel: Fix segfault with PEBS-via-PT with sample_freq

Currently, using PEBS-via-PT with a sample frequency instead of a sample
period, causes a segfault.  For example:

    BUG: kernel NULL pointer dereference, address: 0000000000000195
    <NMI>
    ? __die_body.cold+0x19/0x27
    ? page_fault_oops+0xca/0x290
    ? exc_page_fault+0x7e/0x1b0
    ? asm_exc_page_fault+0x26/0x30
    ? intel_pmu_pebs_event_update_no_drain+0x40/0x60
    ? intel_pmu_pebs_event_update_no_drain+0x32/0x60
    intel_pmu_drain_pebs_icl+0x333/0x350
    handle_pmi_common+0x272/0x3c0
    intel_pmu_handle_irq+0x10a/0x2e0
    perf_event_nmi_handler+0x2a/0x50

That happens because intel_pmu_pebs_event_update_no_drain() assumes all the
pebs_enabled bits represent counter indexes, which is not always the case.
In this particular case, bits 60 and 61 are set for PEBS-via-PT purposes.

The behaviour of PEBS-via-PT with sample frequency is questionable because
although a PMI is generated (PEBS_PMI_AFTER_EACH_RECORD), the period is not
adjusted anyway.

Putting that aside, fix intel_pmu_pebs_event_update_no_drain() by passing
the mask of counter bits instead of 'size'.  Note, prior to the Fixes
commit, 'size' would be limited to the maximum counter index, so the issue
was not hit.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-38055?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-38055?

Apply the vendor's patch.

## Is CVE-2025-38055 being exploited?

There is no known exploitation of CVE-2025-38055 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-2025-38055 and fix it if it is affected.

What it is: CVE-2025-38055 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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-2025-38055 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-2025-38055/ (Markdown: https://insights.sbomify.com/CVE-2025-38055/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38055
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38055
- OSV: https://osv.dev/vulnerability/CVE-2025-38055

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38055/
Summaries are generated and may contain mistakes; the official description above is the record.