CVE-2025-68785

None

CVSS

—

EPSS

0.2%

Published

Jan 13, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A bug in the Linux kernel's virtual networking code could let a local program crash the system or read memory it should not by sending badly formed network instructions.

Exploitation: Local Privilege
Attacker needs: Low Privilege
Complexity: Moderate
Impact: Data Exposure
Component: OS kernel
Class: Improper Input Validation
Remediation: Patch
Effort: Medium
Patch risk: Low

What it actually does

Missing validation of the middle OVS_KEY_ATTR_NSH attribute in push_nsh() allows a malformed netlink action to trigger an out-of-bounds read during later nsh_hdr_from_nlattr execution when the kernel allocates a precisely sized buffer.

Why it matters to the business

Systems running affected Open vSwitch kernels can experience kernel crashes or memory corruption when processing specially crafted network actions, leading to denial of service for virtual networking and potential local privilege escalation on multi-tenant hosts.

How an attack unfolds

An attacker with the ability to execute ovs_packet_cmd_execute or equivalent netlink operations crafts a PUSH_NSH action containing an incorrectly sized or typed middle attribute. The kernel accepts the action during validation but later dereferences invalid memory when executing the action, causing KASAN-detected slab-out-of-bounds access.

How to fix it

Upgrade the Linux kernel to a version containing commit d0c135b8bbbcf92836068fd395bebeb7ae6c7bef or later. Rebuild and reinstall any out-of-tree Open vSwitch modules after the kernel update.

How to confirm the fix worked

Confirm the running kernel contains commit d0c135b8bbbcf92836068fd395bebeb7ae6c7bef or a backport that adds the missing attribute-size and single-attribute checks in validate_push_nsh(). Test by replaying a minimal malformed PUSH_NSH action and verifying the kernel no longer reports KASAN errors.

Typical attack path

Obtain capability to send crafted OVS netlink messages (local user, container, or compromised process)
Construct OVS_ACTION_ATTR_PUSH_NSH with malformed OVS_KEY_ATTR_NSH child attribute
Submit action via ovs_packet_cmd_execute or equivalent
Trigger action execution path that performs unsafe double-unwrap and memcpy

How to detect it

Review kernel logs for KASAN or slab-out-of-bounds reports naming nsh_hdr_from_nlattr, push_nsh, or do_execute_actions. Correlate with processes that recently called ovs_packet_cmd_execute or genl_family_rcv_msg on the OVS genl family.

What your security team should do

Prioritize kernel upgrades on all hosts running Open vSwitch
Restrict unprivileged access to OVS netlink sockets via AppArmor, SELinux, or user namespaces
Monitor for kernel oops or KASAN reports involving nsh_hdr_from_nlattr and push_nsh

The record

In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: fix middle attribute validation in push_nsh() action The push_nsh() action structure looks like this: OVS_ACTION_ATTR_PUSH_NSH(OVS_KEY_ATTR_NSH(OVS_NSH_KEY_ATTR_BASE,...)) The outermost OVS_ACTION_ATTR_PUSH_NSH attribute is OK'ed by the nla_for_each_nested() inside __ovs_nla_copy_actions(). The innermost OVS_NSH_KEY_ATTR_BASE/MD1/MD2 are OK'ed by the nla_for_each_nested() inside nsh_key_put_from_nlattr(). But nothing checks if the attribute in the middle is OK. We don't even check that this attribute is the OVS_KEY_ATTR_NSH. We just do a double unwrap with a pair of nla_data() calls - first time directly while calling validate_push_nsh() and the second time as part of the nla_for_each_nested() macro, which isn't safe, potentially causing invalid memory access if the size of this attribute is incorrect. The failure may not be noticed during validation due to larger netlink buffer, but cause trouble later during action execution where the buffer is allocated exactly to the size: BUG: KASAN: slab-out-of-bounds in nsh_hdr_from_nlattr+0x1dd/0x6a0 [openvswitch] Read of size 184 at addr ffff88816459a634 by task a.out/22624 CPU: 8 UID: 0 PID: 22624 6.18.0-rc7+ #115 PREEMPT(voluntary) Call Trace: <TASK> dump_stack_lvl+0x51/0x70 print_address_description.constprop.0+0x2c/0x390 kasan_report+0xdd/0x110 kasan_check_range+0x35/0x1b0 __asan_memcpy+0x20/0x60 nsh_hdr_from_nlattr+0x1dd/0x6a0 [openvswitch] push_nsh+0x82/0x120 [openvswitch] do_execute_actions+0x1405/0x2840 [openvswitch] ovs_execute_actions+0xd5/0x3b0 [openvswitch] ovs_packet_cmd_execute+0x949/0xdb0 [openvswitch] genl_family_rcv_msg_doit+0x1d6/0x2b0 genl_family_rcv_msg+0x336/0x580 genl_rcv_msg+0x9f/0x130 netlink_rcv_skb+0x11f/0x370 genl_rcv+0x24/0x40 netlink_unicast+0x73e/0xaa0 netlink_sendmsg+0x744/0xbf0 __sys_sendto+0x3d6/0x450 do_syscall_64+0x79/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> Let's add some checks that the attribute is properly sized and it's the only one attribute inside the action. Technically, there is no real reason for OVS_KEY_ATTR_NSH to be there, as we know that we're pushing an NSH header already, it just creates extra nesting, but that's how uAPI works today. So, keeping as it is.

Affected packages

Ecosystem	Package	Introduced	Fixed
Linux	Kernel	4.15.0	5.10.248
Mageia:9	kernel	0	6.6.120-1.mga9
Mageia:9	kernel-linus	0	6.6.120-1.mga9
Mageia:9	kmod-virtualbox	0	7.1.14-14.mga9
Mageia:9	kmod-xtables-addons	0	3.24-88.mga9
openSUSE:Leap 16.0	dtb-aarch64	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-64kb	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-azure	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-default	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-default-base	0	6.12.0-160000.27.1.160000.2.8
openSUSE:Leap 16.0	kernel-docs	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-kvmsmall	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-obs-build	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-obs-qa	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-rt	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-source	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-syms	0	6.12.0-160000.27.1
openSUSE:Leap 16.0	kernel-zfcpdump	0	6.12.0-160000.27.1