# CVE-2026-98151: bpf: Fix REG INVARIANTS VIOLATION on speculative pointer arithmetic

> A logic error in the Linux kernel BPF verifier allows unprivileged users to trigger a warning and potential denial of service via speculative pointer arithmetic.

- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98151, DEBIAN-CVE-2026-98151, GHSA-6969-2pr3-9qx5, UBUNTU-CVE-2026-98151

## What is CVE-2026-98151?

CVE-2026-98151 is a medium-severity vulnerability in Linux kernel, 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 REG INVARIANTS VIOLATION on speculative pointer arithmetic

Take the following unprivileged program as an example:

	r0 = bpf_map_lookup_elem(...)	/* PTR_TO_MAP_VALUE, offset 0 */
	...
	14: r0 += r1			/* r1 is a bounded scalar */
	15: r9 = r0

Loading it triggers a verifier warning from reg_bounds_sanity_check():

	verifier bug: REG INVARIANTS VIOLATION (alu): const subreg tnum out
	of sync with range bounds r64={.base=0x0, .size=0x0}
	r32={.base=0x0, .size=0xffffffff} var_off=(0x0, 0x0)

What happens:

1. Processing insn 14 (r0 += r1) in adjust_ptr_min_max_vals(), the new
   offset is computed into dst_reg's var_off and 32/64-bit ranges.

2. Because pointer registers do not track 32-bit subregister bounds,
   __mark_reg32_unbounded() first sets r32 to the full range; r32 is
   re-derived from the offset at the end of the function by
   reg_bounds_sync().

3. On the unprivileged path, sanitize_ptr_alu() is called and, via
   sanitize_speculative_path() -> push_stack(), snapshots the current
   register state and schedules the next instruction (insn 15) to be
   verified directly as a speculative path.

4. That snapshot is taken between step 2 and the final reg_bounds_sync():
   at this point dst_reg's var_off still holds the (const) original
   offset while r32 has just been blanked to the full range, i.e. the two
   are out of sync. When the speculative path later verifies insn 15
   (r9 = r0), the inconsistent state reaches reg_bounds_sanity_check() and
   trips the warning.

var_off and the 32-bit range must always be consistent. There are two
ways to keep the snapshot consistent:

  1. sync var_off and r32 before the snapshot so they match, or
  2. leave r32 at its original (already consistent) value and blank it
     only after the snapshot.

The whole point of sanitize_ptr_alu() is to insert a harmless masking
sequence that keeps the access in bounds under speculation, so the state
it snapshots should faithfully represent that. Take approach 2: move
__mark_reg32_unbounded() to after sanitize_ptr_alu(), so the speculative
snapshot keeps the pointer's original, consistent r32. The non-speculative
path is unchanged: r32 is still blanked before the offset is applied and
re-derived by reg_bounds_sync().

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2026-98151?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-98151?

Apply the vendor's patch.

## Is CVE-2026-98151 being exploited?

There is no known exploitation of CVE-2026-98151 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-2026-98151 and fix it if it is affected.

What it is: CVE-2026-98151 is a medium-severity vulnerability in Linux kernel, 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-2026-98151 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-2026-98151/ (Markdown: https://insights.sbomify.com/CVE-2026-98151/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98151
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98151
- OSV: https://osv.dev/vulnerability/CVE-2026-98151

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98151/
Summaries are generated and may contain mistakes; the official description above is the record.