# CVE-2026-99141: tracing: Fix crash in print_graph_function_event()


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-99141, GHSA-jfp7-c7j3-v9pj, UBUNTU-CVE-2026-99141

## What is CVE-2026-99141?

CVE-2026-99141 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

tracing: Fix crash in print_graph_function_event()

tracing_set_tracer() assigns the flags of the newly selected tracer
with:

	tr->current_trace_flags = t->flags ? : t->tracer->flags;

If the new tracer defines neither static flags nor default flags, like
hwlat, irqsoff or wakeup, add_tracer() has no per instance flags copy
for it, and both operands are NULL, so tr->current_trace_flags ends up
being NULL as well.

The ring buffer is not cleared when switching tracers: it is reset
inside tracer_init(), after current_trace_flags was already assigned.
If the buffer still holds function_graph entries of the previous
tracer, printing one of them dereferences the NULL pointer. This was
hit by cat trace during an ftrace stress test:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor read access in kernel mode
  RIP: 0010:print_graph_function_event+0xe/0x20
  Call Trace:
   s_show+0x4d/0x110
   seq_read_iter+0x2d4/0x490
   seq_read+0x130/0x170
   vfs_read+0xb5/0x370
   ksys_read+0x6d/0xe0
   do_syscall_64+0xbc/0x450

The snapshot buffer is not reset at all, so this can be reproduced
without a race:

  echo function_graph > /sys/kernel/tracing/current_tracer
  echo 1 > /sys/kernel/tracing/snapshot
  echo hwlat > /sys/kernel/tracing/current_tracer
  cat /sys/kernel/tracing/snapshot

Rather than teaching every user of tr->current_trace_flags about this
corner case, make sure it is never NULL: when the newly selected
tracer has no flags at all, tracing_set_tracer() falls back to a
static empty no_tracer_flags. run_tracer_selftest() can hit the same
case, so the same fallback is added there too. The existing users
already handle opts == NULL, so these tracers keep behaving as before.

## Which versions are affected by CVE-2026-99141?


## How do I fix CVE-2026-99141?

Upgrade to a fixed version.

## Is CVE-2026-99141 being exploited?

There is no known exploitation of CVE-2026-99141 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99141 and fix it if it is affected.

What it is: CVE-2026-99141 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99141 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-2026-99141/ (Markdown: https://insights.sbomify.com/CVE-2026-99141/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99141
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99141
- OSV: https://osv.dev/vulnerability/CVE-2026-99141

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99141/
Summaries are generated and may contain mistakes; the official description above is the record.