# CVE-2026-98950: flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect()


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** AZL-110756, BELL-CVE-2026-98950, DEBIAN-CVE-2026-98950, GHSA-4jwg-g8h6-9gv7, UBUNTU-CVE-2026-98950

## What is CVE-2026-98950?

CVE-2026-98950 is a vulnerability in Linux, published on 23 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect()

bpf_flow_dissect() sanitizes the offsets returned by the BPF program
with clamp_t(u16, ..., hlen).

If hlen is bigger than 65535, the upper bound is truncated before
the comparison. For instance, with hlen == 65536, both nhoff and
thoff are forced to zero, even if the program returned sane values.

This is the same class of bug as the one fixed in commit 99bda1ecbd56
("flow_dissector: avoid u16 truncation of skb->len when computing
thoff"). That fix does not cover the BPF path, because
__skb_flow_dissect() returns early when a BPF flow dissector
handles the packet.

struct bpf_flow_keys stores nhoff and thoff as u16, so cap hlen
to U16_MAX before clamping.

Found by sashiko while reviewing the commit above.

## Which versions are affected by CVE-2026-98950?


## How do I fix CVE-2026-98950?

Upgrade to a fixed version.

## Is CVE-2026-98950 being exploited?

There is no known exploitation of CVE-2026-98950 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98950 and fix it if it is affected.

What it is: CVE-2026-98950 is a vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98950 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-2026-98950/ (Markdown: https://insights.sbomify.com/CVE-2026-98950/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98950
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98950
- OSV: https://osv.dev/vulnerability/CVE-2026-98950

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98950/
Summaries are generated and may contain mistakes; the official description above is the record.