# CVE-2026-98044: bpf: Reject legacy packet loads from callbacks

> A privileged user can trigger a verifier bug via legacy BPF packet loads in callbacks, causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104184, BELL-CVE-2026-98044, DEBIAN-CVE-2026-98044, GHSA-wq8m-pjjr-x46w, UBUNTU-CVE-2026-98044

## What is CVE-2026-98044?

CVE-2026-98044 is a denial of service 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: Reject legacy packet loads from callbacks

check_ld_abs() models a failed BPF_LD_ABS or BPF_LD_IND in a
subprogram as an implicit return with R0 set to zero. It calls
prepare_func_exit() to explore this synthesized path.

When the load is reached directly from a synchronous callback,
prepare_func_exit() enforces the callback return contract and marks R0
precise. R0 is not derived from a real instruction on this path, so
precision backtracking reaches the callback call with R0 still requested
and triggers the "callback unexpected regs" verifier bug. A privileged
program loader can therefore cause a verifier warning and an -EFAULT
BPF_PROG_LOAD.

These legacy packet-load instructions are deprecated. Reject them from
callbacks rather than complicating their implicit-return model. Check all
active frames before constructing the implicit return so nested static
subprograms cannot hide the callback context.

Global functions are verified independently with a fresh frame zero, so
an active-frame check cannot identify a global function called from a
callback. Also check the complete subprogram call graph during stack-depth
validation and reject a function containing a legacy load when any caller
is a callback. This covers global and static descendants without making
has_ld_abs transitive, preserving its per-function BTF return-type check.
Ordinary uses outside callbacks remain supported.

## Which versions are affected by CVE-2026-98044?


## How do I fix CVE-2026-98044?

Apply the vendor's patch.

## Is CVE-2026-98044 being exploited?

There is no known exploitation of CVE-2026-98044 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98044 and fix it if it is affected.

What it is: CVE-2026-98044 is a denial of service 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-2026-98044 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-2026-98044/ (Markdown: https://insights.sbomify.com/CVE-2026-98044/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98044
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98044
- OSV: https://osv.dev/vulnerability/CVE-2026-98044

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98044/
Summaries are generated and may contain mistakes; the official description above is the record.