# CVE-2024-42096: x86: stop playing stack games in profile_pc()

> A flaw in the Linux kernel's timer-based profiling code could trigger KASAN warnings and potential instability due to invalid stack layout assumptions.

- **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:** 29 Jul 2024
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2024-42096, DEBIAN-CVE-2024-42096, GHSA-vjj3-m2jf-2pfq, UBUNTU-CVE-2024-42096

## What is CVE-2024-42096?

CVE-2024-42096 is a medium-severity vulnerability in Linux kernel, published on 29 Jul 2024. 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:

x86: stop playing stack games in profile_pc()

The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that relevant any more to begin with, but it also ends
up making assumptions based on the stack layout that aren't necessarily
valid.

Basically, the code tries to account the time spent in spinlocks to the
caller rather than the spinlock, and while I support that as a concept,
it's not worth the code complexity or the KASAN warnings when no serious
profiling is done using timers anyway these days.

And the code really does depend on stack layout that is only true in the
simplest of cases.  We've lost the comment at some point (I think when
the 32-bit and 64-bit code was unified), but it used to say:

	Assume the lock function has either no stack frame or a copy
	of eflags from PUSHF.

which explains why it just blindly loads a word or two straight off the
stack pointer and then takes a minimal look at the values to just check
if they might be eflags or the return pc:

	Eflags always has bits 22 and up cleared unlike kernel addresses

but that basic stack layout assumption assumes that there isn't any lock
debugging etc going on that would complicate the code and cause a stack
frame.

It causes KASAN unhappiness reported for years by syzkaller [1] and
others [2].

With no real practical reason for this any more, just remove the code.

Just for historical interest, here's some background commits relating to
this code from 2006:

  0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels")
  31679f38d886 ("Simplify profile_pc on x86-64")

and a code unification from 2009:

  ef4512882dbe ("x86: time_32/64.c unify profile_pc")

but the basics of this thing actually goes back to before the git tree.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2024-42096?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-42096?

Apply the vendor's patch.

## Is CVE-2024-42096 being exploited?

There is no known exploitation of CVE-2024-42096 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-2024-42096 and fix it if it is affected.

What it is: CVE-2024-42096 is a medium-severity vulnerability in Linux kernel, published on 29 Jul 2024. 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-2024-42096 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-2024-42096/ (Markdown: https://insights.sbomify.com/CVE-2024-42096/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-42096
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-42096
- OSV: https://osv.dev/vulnerability/CVE-2024-42096

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-42096/
Summaries are generated and may contain mistakes; the official description above is the record.