# CVE-2026-98584: net/sched: fix potential stack infoleak in em_text_dump()

> A local attacker can read uninitialized kernel stack memory via netlink filter dumps, potentially exposing sensitive data.

- **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:** BELL-CVE-2026-98584, DEBIAN-CVE-2026-98584, GHSA-r555-rgvq-cqv7, UBUNTU-CVE-2026-98584

## What is CVE-2026-98584?

CVE-2026-98584 is a 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: fix potential stack infoleak in em_text_dump()

em_text_dump() allocates struct tcf_em_text on the stack without zeroing
it.  strscpy() writes the algorithm name and a NUL terminator into
conf.algo[], leaving the remaining bytes uninitialised.  nla_put_nohdr()
then copies the full struct to the netlink response.

KMSAN on Linux 7.2-rc6 reports two kernel-infoleak splats from this path,
one triggered via "tc filter show" and one via a raw RTM_GETTFILTER dump:

  BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x1c9/0x2620
    nla_put_nohdr+0x83/0x130
    em_text_dump+0x291/0x550
  Local variable conf created at: em_text_dump+0x5d/0x550
  Bytes 168-179 of 199 are uninitialized

I am not certain whether this constitutes a real security problem in
practice: the test was conducted in a controlled KMSAN environment and
the leaked stack bytes may or may not carry sensitive data on actual
production kernels.  I am reporting it because KMSAN flagged it as a
kernel-infoleak and the fix is straightforward.  I can provide a
userspace reproducer on request.

The original code used strncpy() which zero-pads to the destination size.
Commit b04202d6065c ("net/sched: replace strncpy with strscpy") replaced
it with strscpy(), which does not pad, creating this condition.
Zero-initialising the struct closes it.

## Which versions are affected by CVE-2026-98584?


## How do I fix CVE-2026-98584?

Apply the vendor's patch.

## Is CVE-2026-98584 being exploited?

There is no known exploitation of CVE-2026-98584 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98584 and fix it if it is affected.

What it is: CVE-2026-98584 is a 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-2026-98584 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-2026-98584/ (Markdown: https://insights.sbomify.com/CVE-2026-98584/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98584
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98584
- OSV: https://osv.dev/vulnerability/CVE-2026-98584

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98584/
Summaries are generated and may contain mistakes; the official description above is the record.