# CVE-2026-43086: ipvs: fix NULL deref in ip_vs_add_service error path

> A NULL pointer dereference in the Linux kernel IPVS module allows local attackers to cause a system crash via a specific error path in service addition.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 6 May 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-43086, DEBIAN-CVE-2026-43086, GHSA-hg4p-7h98-9fmh, ROOT-OS-UBUNTU-2404-CVE-2026-43086, UBUNTU-CVE-2026-43086

## What is CVE-2026-43086?

CVE-2026-43086 is a medium-severity vulnerability in Linux kernel, published on 6 May 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: fix NULL deref in ip_vs_add_service error path

When ip_vs_bind_scheduler() succeeds in ip_vs_add_service(), the local
variable sched is set to NULL.  If ip_vs_start_estimator() subsequently
fails, the out_err cleanup calls ip_vs_unbind_scheduler(svc, sched)
with sched == NULL.  ip_vs_unbind_scheduler() passes the cur_sched NULL
check (because svc->scheduler was set by the successful bind) but then
dereferences the NULL sched parameter at sched->done_service, causing a
kernel panic at offset 0x30 from NULL.

 Oops: general protection fault, [..] [#1] PREEMPT SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
 RIP: 0010:ip_vs_unbind_scheduler (net/netfilter/ipvs/ip_vs_sched.c:69)
 Call Trace:
  <TASK>
  ip_vs_add_service.isra.0 (net/netfilter/ipvs/ip_vs_ctl.c:1500)
  do_ip_vs_set_ctl (net/netfilter/ipvs/ip_vs_ctl.c:2809)
  nf_setsockopt (net/netfilter/nf_sockopt.c:102)
  [..]

Fix by simply not clearing the local sched variable after a successful
bind.  ip_vs_unbind_scheduler() already detects whether a scheduler is
installed via svc->scheduler, and keeping sched non-NULL ensures the
error path passes the correct pointer to both ip_vs_unbind_scheduler()
and ip_vs_scheduler_put().

While the bug is older, the problem popups in more recent kernels (6.2),
when the new error path is taken after the ip_vs_start_estimator() call.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-43086?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43086?

Apply the vendor's patch.

## Is CVE-2026-43086 being exploited?

There is no known exploitation of CVE-2026-43086 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43086 and fix it if it is affected.

What it is: CVE-2026-43086 is a medium-severity vulnerability in Linux kernel, published on 6 May 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-2026-43086 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43086/ (Markdown: https://insights.sbomify.com/CVE-2026-43086/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43086
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43086
- OSV: https://osv.dev/vulnerability/CVE-2026-43086

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43086/
Summaries are generated and may contain mistakes; the official description above is the record.