# CVE-2026-46132: net: rtnetlink: zero ifla_vf_broadcast to avoid stack infoleak in rtnl_fill_vfinfo

> Uninitialized kernel stack memory is leaked to userspace via netlink, allowing local attackers to read sensitive data like return addresses.

- **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:** 28 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-88851, BELL-CVE-2026-46132, DEBIAN-CVE-2026-46132, GHSA-m5g9-vgm2-5cvw, ROOT-OS-DEBIAN-11-CVE-2026-46132, ROOT-OS-DEBIAN-12-CVE-2026-46132, ROOT-OS-UBUNTU-2204-CVE-2026-46132, ROOT-OS-UBUNTU-2404-CVE-2026-46132, UBUNTU-CVE-2026-46132

## What is CVE-2026-46132?

CVE-2026-46132 is a medium-severity vulnerability in Linux kernel, published on 28 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:

net: rtnetlink: zero ifla_vf_broadcast to avoid stack infoleak in rtnl_fill_vfinfo

rtnl_fill_vfinfo() declares struct ifla_vf_broadcast on the stack
without initialisation:

	struct ifla_vf_broadcast vf_broadcast;

The struct contains a single fixed 32-byte field:

	/* include/uapi/linux/if_link.h */
	struct ifla_vf_broadcast {
		__u8 broadcast[32];
	};

The function then copies dev->broadcast into it using dev->addr_len
as the length:

	memcpy(vf_broadcast.broadcast, dev->broadcast, dev->addr_len);

On Ethernet devices (the overwhelming majority of SR-IOV NICs)
dev->addr_len is 6, so only the first 6 bytes of broadcast[] are
written. The remaining 26 bytes retain whatever was previously on
the kernel stack. The full struct is then handed to userspace via:

	nla_put(skb, IFLA_VF_BROADCAST,
		sizeof(vf_broadcast), &vf_broadcast)

leaking up to 26 bytes of uninitialised kernel stack per VF per
RTM_GETLINK request, repeatable.

The other vf_* structs in the same function are explicitly zeroed
for exactly this reason - see the memset() calls for ivi,
vf_vlan_info, node_guid and port_guid a few lines above.
vf_broadcast was simply missed when it was added.

Reachability: any unprivileged local process can open AF_NETLINK /
NETLINK_ROUTE without capabilities and send RTM_GETLINK with an
IFLA_EXT_MASK attribute carrying RTEXT_FILTER_VF. The kernel walks
each VF and emits IFLA_VF_BROADCAST, leaking 26 bytes of stack per
VF per request. Stack residue at this call site can include return
addresses and transient sensitive data; KASAN with stack
instrumentation, or KMSAN, will flag the nla_put() when reproduced.

Zero the on-stack struct before the partial memcpy, matching the
existing pattern used for the other vf_* structs in the same
function.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2026-46132?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46132?

Apply the vendor's patch.

## Is CVE-2026-46132 being exploited?

There is no known exploitation of CVE-2026-46132 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-2026-46132 and fix it if it is affected.

What it is: CVE-2026-46132 is a medium-severity vulnerability in Linux kernel, published on 28 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-2026-46132 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-2026-46132/ (Markdown: https://insights.sbomify.com/CVE-2026-46132/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46132
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46132
- OSV: https://osv.dev/vulnerability/CVE-2026-46132

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46132/
Summaries are generated and may contain mistakes; the official description above is the record.