# CVE-2026-98794: ipvs: filter some flags received in the backup server

> A malicious actor on the network can cause denial of service in Linux IPVS backup servers by sending crafted synchronization messages with invalid flag combinations.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108878, BELL-CVE-2026-98794, DEBIAN-CVE-2026-98794, GHSA-c8w6-8f9f-2m9q, UBUNTU-CVE-2026-98794

## What is CVE-2026-98794?

CVE-2026-98794 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:

ipvs: filter some flags received in the backup server

While the IPVS SYNC protocol is not secure by design
we can still protect the backup server from messages that
can wreak havoc.

This commit addresses problems from received connection flags
or their combinations. We now drop messages as follows:

1. the NO_CPORT+TEMPLATE combination allows lookups for normal
connections to hit template which can break in many ways.
While the master does not sync connections with NO_CPORT flag,
i.e. before they are established, we still accept NO_CPORT
without TEMPLATE.

2. ONE_PACKET: it is not sent by master, so we do not
expect it in backup. Before now it was ignored by
IP_VS_CONN_F_BACKUP_MASK for protocol v1 while protocol
v0 created connections that are not hashed and dropped
immediately. Better to apply the IP_VS_CONN_F_BACKUP_MASK
also to the flags from v0 messages for consistency with v1.

## Which versions are affected by CVE-2026-98794?


## How do I fix CVE-2026-98794?

Apply the vendor's patch.

## Is CVE-2026-98794 being exploited?

There is no known exploitation of CVE-2026-98794 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98794 and fix it if it is affected.

What it is: CVE-2026-98794 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-2026-98794 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-2026-98794/ (Markdown: https://insights.sbomify.com/CVE-2026-98794/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98794
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98794
- OSV: https://osv.dev/vulnerability/CVE-2026-98794

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98794/
Summaries are generated and may contain mistakes; the official description above is the record.