# CVE-2026-98063: bpf: Fix NULL-ptr-deref in btf_var_show()

> A local attacker with BPF privileges can trigger a kernel crash via a NULL pointer dereference in the BTF subsystem.

- **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-104492, BELL-CVE-2026-98063, DEBIAN-CVE-2026-98063, GHSA-h366-qqqg-44v8, UBUNTU-CVE-2026-98063

## What is CVE-2026-98063?

CVE-2026-98063 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 in btf_var_show()

btf_var_show() calls btf_type_id_resolve() unconditionally, which
dereferences btf->resolved_ids. That is NULL for a base BTF - e.g. the
vmlinux BTF that bpf_snprintf_btf() renders against - since base BTF is
not resolved during parsing. btf_modifier_show() guards this with
'if (btf->resolved_ids)', but btf_var_show() does not.

A BPF program that passes the type_id of a BTF_KIND_VAR from the vmlinux
BTF to bpf_snprintf_btf() thus NULL-derefs:

KASAN: probably user-memory-access in range [0x46638-0x4663f]
RIP: 0010:btf_var_show (kernel/bpf/btf.c:2929)
Call Trace:
 <TASK>
 btf_type_show (kernel/bpf/btf.c:8259)
 btf_type_snprintf_show (kernel/bpf/btf.c:8329)
 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:84)
 entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
 </TASK>

Resolve the var's type directly with btf_type_skip_modifiers() when
resolved_ids is NULL, mirroring btf_modifier_show().

## Which versions are affected by CVE-2026-98063?


## How do I fix CVE-2026-98063?

Apply the vendor's patch.

## Is CVE-2026-98063 being exploited?

There is no known exploitation of CVE-2026-98063 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98063 and fix it if it is affected.

What it is: CVE-2026-98063 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-2026-98063 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-2026-98063/ (Markdown: https://insights.sbomify.com/CVE-2026-98063/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98063
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98063
- OSV: https://osv.dev/vulnerability/CVE-2026-98063

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98063/
Summaries are generated and may contain mistakes; the official description above is the record.