CVE-2026-89488

Received Received - Intake

Use-After-Free in Open vSwitch Kernel Module

Publication date: 2026-09-11

Last updated on: 2026-09-14

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: openvswitch: Fix CT limit teardown use-after-free Packet processing uses CT limit state under RCU, while netns teardown frees that state under ovs_mutex. The CT limit pointer was neither removed from readers nor protected by a grace period, allowing packet processing to dereference the freed state. An unprivileged user can trigger this bug from a user and network namespace, causing a slab-use-after-free in ovs_ct_execute() when the netns is torn down. Publish the CT limit pointer through RCU, remove it before teardown, and wait for readers before freeing its contents. Keep ovs_mutex around individual CT limit updates, and use the RCU read-side lock while GET traverses the RCU-protected limit lists. Netns teardown detaches the RCU-protected CT limit state in the pernet .pre_exit callback while holding ovs_mutex. The pernet core guarantees an RCU grace period between the .pre_exit and .exit callbacks, so the .exit callback completes the teardown without adding any extra synchronization. The netlink command handlers do not need NULL checks because the userspace netlink socket holds an active reference to its network namespace while a request is processed. The per-netns exit path therefore cannot run concurrently with SET, DEL, or GET for that socket's namespace.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-14

Generated

2026-10-02

AI Q&A

2026-09-12

EPSS Evaluated

2026-10-01

NVD

CVE-2026-89488

EUVD

EUVD-2026-76394

Affected Vendors & Products

Vendor	Product	Version / Range
openvswitch	openvswitch	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free flaw in the Linux kernel's Open vSwitch (OVS) module. It occurs during network namespace teardown when a CT (Connection Tracking) limit state is freed while still being accessed by packet processing under RCU (Read-Copy-Update). An unprivileged user can trigger this by operating in a user and network namespace, leading to a slab-use-after-free in ovs_ct_execute().

Detection Guidance

This vulnerability may not have direct detection commands as it requires specific kernel conditions. Monitor kernel logs for slab-use-after-free errors or crashes in openvswitch modules. Check for netns teardown issues during packet processing. Use 'dmesg' or 'journalctl -k' to look for related errors.

Impact Analysis

This vulnerability allows an unprivileged user to cause a system crash or potentially execute arbitrary code with kernel privileges. It could lead to denial-of-service conditions or unauthorized access to sensitive system resources.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a low-level kernel memory corruption issue in Open vSwitch that could lead to system instability or crashes but does not involve data exposure or unauthorized access to sensitive information.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves this issue. If immediate patching is not possible, restrict unprivileged user access to network namespaces and avoid running openvswitch in environments with untrusted users.

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