# CVE-2025-38493: tracing/osnoise: Fix crash in timerlat_dump_stack()

> A local attacker can trigger a kernel panic in the Linux kernel's osnoise tracer by exploiting a buffer overflow in timerlat_dump_stack, causing a denial of service.

- **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:** 28 Jul 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-65946, BELL-CVE-2025-38493, DEBIAN-CVE-2025-38493, GHSA-2xmx-r7cc-9x6c, ROOT-OS-UBUNTU-2404-CVE-2025-38493, UBUNTU-CVE-2025-38493

## What is CVE-2025-38493?

CVE-2025-38493 is a medium-severity denial of service vulnerability in Linux kernel, published on 28 Jul 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:

tracing/osnoise: Fix crash in timerlat_dump_stack()

We have observed kernel panics when using timerlat with stack saving,
with the following dmesg output:

memcpy: detected buffer overflow: 88 byte write of buffer size 0
WARNING: CPU: 2 PID: 8153 at lib/string_helpers.c:1032 __fortify_report+0x55/0xa0
CPU: 2 UID: 0 PID: 8153 Comm: timerlatu/2 Kdump: loaded Not tainted 6.15.3-200.fc42.x86_64 #1 PREEMPT(lazy)
Call Trace:
 <TASK>
 ? trace_buffer_lock_reserve+0x2a/0x60
 __fortify_panic+0xd/0xf
 __timerlat_dump_stack.cold+0xd/0xd
 timerlat_dump_stack.part.0+0x47/0x80
 timerlat_fd_read+0x36d/0x390
 vfs_read+0xe2/0x390
 ? syscall_exit_to_user_mode+0x1d5/0x210
 ksys_read+0x73/0xe0
 do_syscall_64+0x7b/0x160
 ? exc_page_fault+0x7e/0x1a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

__timerlat_dump_stack() constructs the ftrace stack entry like this:

struct stack_entry *entry;
...
memcpy(&entry->caller, fstack->calls, size);
entry->size = fstack->nr_entries;

Since commit e7186af7fb26 ("tracing: Add back FORTIFY_SOURCE logic to
kernel_stack event structure"), struct stack_entry marks its caller
field with __counted_by(size). At the time of the memcpy, entry->size
contains garbage from the ringbuffer, which under some circumstances is
zero, triggering a kernel panic by buffer overflow.

Populate the size field before the memcpy so that the out-of-bounds
check knows the correct size. This is analogous to
__ftrace_trace_stack().

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2025-38493?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-38493?

Apply the vendor's patch.

## Is CVE-2025-38493 being exploited?

There is no known exploitation of CVE-2025-38493 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-2025-38493 and fix it if it is affected.

What it is: CVE-2025-38493 is a medium-severity denial of service vulnerability in Linux kernel, published on 28 Jul 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-2025-38493 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-2025-38493/ (Markdown: https://insights.sbomify.com/CVE-2025-38493/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38493
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38493
- OSV: https://osv.dev/vulnerability/CVE-2025-38493

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38493/
Summaries are generated and may contain mistakes; the official description above is the record.