# CVE-2026-98064: bpf: Fix NULL-ptr-deref when showing a void BTF type

> A local attacker with BPF privileges can trigger a kernel crash by passing a void BTF type to bpf_snprintf_btf, causing a null pointer dereference.

- **Severity:** Not scored
- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104391, BELL-CVE-2026-98064, DEBIAN-CVE-2026-98064, GHSA-rf5p-p5fj-r25r, UBUNTU-CVE-2026-98064

## What is CVE-2026-98064?

CVE-2026-98064 is a vulnerability in Linux, published on 25 Sep 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:

bpf: Fix NULL-ptr-deref when showing a void BTF type

btf_modifier_show() resolves the modifier and then calls
btf_type_ops(t)->show() unconditionally. For the void type (type_id 0,
BTF_KIND_UNKN) kind_ops[] has no entry, so ->show is NULL.

A "const void" (a modifier resolving to void) cannot be a map key or
value - map_check_btf() rejects it because void has no size - so the map
dump path does not reach it. But bpf_snprintf_btf() takes a type_id
straight from the BPF program, and passing such a "const void" from the
vmlinux BTF NULL-derefs:

KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
RIP: 0010:btf_modifier_show (kernel/bpf/btf.c:2914)
Call Trace:
 <TASK>
 btf_type_show (kernel/bpf/btf.c:8251)
 btf_type_snprintf_show (kernel/bpf/btf.c:8321)
 bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047)
 bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829)
 __sys_bpf (kernel/bpf/syscall.c:4804)
 do_syscall_64 (arch/x86/entry/syscall_64.c:94)
 entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
 </TASK>

Fall back to btf_df_show() when the resolved type has no show op; it
emits the "<unsupported kind:N>" placeholder already used for kinds like
FWD and FUNC. bpf_snprintf_btf() then returns the length as usual.

## Which versions are affected by CVE-2026-98064?


## How do I fix CVE-2026-98064?

Apply the vendor's patch.

## Is CVE-2026-98064 being exploited?

There is no known exploitation of CVE-2026-98064 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98064 and fix it if it is affected.

What it is: CVE-2026-98064 is a vulnerability in Linux, published on 25 Sep 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-2026-98064 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-2026-98064/ (Markdown: https://insights.sbomify.com/CVE-2026-98064/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98064
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98064
- OSV: https://osv.dev/vulnerability/CVE-2026-98064

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98064/
Summaries are generated and may contain mistakes; the official description above is the record.