# CVE-2023-53798: ethtool: Fix uninitialized number of lanes

> A local attacker with low privileges can trigger uninitialized memory usage in the Linux kernel ethtool interface, potentially leading to information disclosure.

- **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:** 9 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-53798, DEBIAN-CVE-2023-53798, GHSA-rhrj-6hqh-9pgr, UBUNTU-CVE-2023-53798

## What is CVE-2023-53798?

CVE-2023-53798 is a vulnerability in Linux, published on 9 Dec 2025. 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:

ethtool: Fix uninitialized number of lanes

It is not possible to set the number of lanes when setting link modes
using the legacy IOCTL ethtool interface. Since 'struct
ethtool_link_ksettings' is not initialized in this path, drivers receive
an uninitialized number of lanes in 'struct
ethtool_link_ksettings::lanes'.

When this information is later queried from drivers, it results in the
ethtool code making decisions based on uninitialized memory, leading to
the following KMSAN splat [1]. In practice, this most likely only
happens with the tun driver that simply returns whatever it got in the
set operation.

As far as I can tell, this uninitialized memory is not leaked to user
space thanks to the 'ethtool_ops->cap_link_lanes_supported' check in
linkmodes_prepare_data().

Fix by initializing the structure in the IOCTL path. Did not find any
more call sites that pass an uninitialized structure when calling
'ethtool_ops::set_link_ksettings()'.

[1]
BUG: KMSAN: uninit-value in ethnl_update_linkmodes net/ethtool/linkmodes.c:273 [inline]
BUG: KMSAN: uninit-value in ethnl_set_linkmodes+0x190b/0x19d0 net/ethtool/linkmodes.c:333
 ethnl_update_linkmodes net/ethtool/linkmodes.c:273 [inline]
 ethnl_set_linkmodes+0x190b/0x19d0 net/ethtool/linkmodes.c:333
 ethnl_default_set_doit+0x88d/0xde0 net/ethtool/netlink.c:640
 genl_family_rcv_msg_doit net/netlink/genetlink.c:968 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
 genl_rcv_msg+0x141a/0x14c0 net/netlink/genetlink.c:1065
 netlink_rcv_skb+0x3f8/0x750 net/netlink/af_netlink.c:2577
 genl_rcv+0x40/0x60 net/netlink/genetlink.c:1076
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0xf41/0x1270 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x127d/0x1430 net/netlink/af_netlink.c:1942
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg net/socket.c:747 [inline]
 ____sys_sendmsg+0xa24/0xe40 net/socket.c:2501
 ___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555
 __sys_sendmsg net/socket.c:2584 [inline]
 __do_sys_sendmsg net/socket.c:2593 [inline]
 __se_sys_sendmsg net/socket.c:2591 [inline]
 __x64_sys_sendmsg+0x36b/0x540 net/socket.c:2591
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was stored to memory at:
 tun_get_link_ksettings+0x37/0x60 drivers/net/tun.c:3544
 __ethtool_get_link_ksettings+0x17b/0x260 net/ethtool/ioctl.c:441
 ethnl_set_linkmodes+0xee/0x19d0 net/ethtool/linkmodes.c:327
 ethnl_default_set_doit+0x88d/0xde0 net/ethtool/netlink.c:640
 genl_family_rcv_msg_doit net/netlink/genetlink.c:968 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
 genl_rcv_msg+0x141a/0x14c0 net/netlink/genetlink.c:1065
 netlink_rcv_skb+0x3f8/0x750 net/netlink/af_netlink.c:2577
 genl_rcv+0x40/0x60 net/netlink/genetlink.c:1076
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0xf41/0x1270 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x127d/0x1430 net/netlink/af_netlink.c:1942
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg net/socket.c:747 [inline]
 ____sys_sendmsg+0xa24/0xe40 net/socket.c:2501
 ___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555
 __sys_sendmsg net/socket.c:2584 [inline]
 __do_sys_sendmsg net/socket.c:2593 [inline]
 __se_sys_sendmsg net/socket.c:2591 [inline]
 __x64_sys_sendmsg+0x36b/0x540 net/socket.c:2591
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was stored to memory at:
 tun_set_link_ksettings+0x37/0x60 drivers/net/tun.c:3553
 ethtool_set_link_ksettings+0x600/0x690 net/ethtool/ioctl.c:609
 __dev_ethtool net/ethtool/ioctl.c:3024 [inline]
 dev_ethtool+0x1db9/0x2a70 net/ethtool/ioctl.c:3078
 dev_ioctl+0xb07/0x1270 net/core/dev_ioctl.c:524
 sock_do_ioctl+0x295/0x540 net/socket.c:1213
 sock_i
---truncated---

## Which versions are affected by CVE-2023-53798?


## How do I fix CVE-2023-53798?

Apply the vendor's patch.

## Is CVE-2023-53798 being exploited?

There is no known exploitation of CVE-2023-53798 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-53798 and fix it if it is affected.

What it is: CVE-2023-53798 is a vulnerability in Linux, published on 9 Dec 2025. 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-2023-53798 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-2023-53798/ (Markdown: https://insights.sbomify.com/CVE-2023-53798/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53798
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53798
- OSV: https://osv.dev/vulnerability/CVE-2023-53798

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53798/
Summaries are generated and may contain mistakes; the official description above is the record.