# CVE-2026-98622: net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure

> An unprivileged user can crash the system by racing conntrack flushes with traffic control actions if panic_on_warn is enabled.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108686, BELL-CVE-2026-98622, DEBIAN-CVE-2026-98622, GHSA-qg6m-cv4g-hx6q, UBUNTU-CVE-2026-98622

## What is CVE-2026-98622?

CVE-2026-98622 is a denial of service vulnerability in Linux, published on 18 Oct 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:

net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure

flow_offload_alloc() returns NULL when the conntrack entry is dying
(e.g. raced with a conntrack flush) or when the GFP_ATOMIC allocation
fails; both are expected under load and neither is a kernel bug. This
path runs from softirq on every committed packet, so with
panic_on_warn=1 an unprivileged user can panic the box just by racing
a conntrack flush against a `tc ... action ct commit` classifier.

Reproduced with a custom repro under QEMU: a small, fixed set of UDP
flows through `tc filter ... action ct commit` on lo, raced against
threads flooding bare ctnetlink CT_DELETE (flush) requests. Hits
WARNING: net/sched/act_ct.c:437 (tcf_ct_flow_table_add(), inlined
into tcf_ct_act() in this build) within ~15s on the unpatched kernel;
same setup is clean on the patched kernel. The fix itself is
behavior-preserving: both branches already did `goto err_alloc`
before and after, only the WARN is removed.

## Which versions are affected by CVE-2026-98622?


## How do I fix CVE-2026-98622?

Apply the vendor's patch.

## Is CVE-2026-98622 being exploited?

There is no known exploitation of CVE-2026-98622 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98622 and fix it if it is affected.

What it is: CVE-2026-98622 is a denial of service vulnerability in Linux, published on 18 Oct 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-2026-98622 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-2026-98622/ (Markdown: https://insights.sbomify.com/CVE-2026-98622/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98622
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98622
- OSV: https://osv.dev/vulnerability/CVE-2026-98622

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98622/
Summaries are generated and may contain mistakes; the official description above is the record.