CVE-2026-64027
Received Received - Intake

Use-After-Free in Linux Kernel Net Shaper

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant. The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU. Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-64027
EUVD
EUVD-2026-45600

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
linux linux_kernel *
linux_kernel linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is a race condition in the Linux kernel's network traffic shaper (net: shaper). It occurs due to non-atomic flag storage in the XArray data structure. When a reader sees a VALID mark for an entry, gets interrupted, and a writer replaces the entry with a different one, the reader may fetch the wrong entry. This can lead to a use-after-free (UAF) vulnerability because net_shaper_rollback() assumes entries without VALID can be safely freed without observing RCU.

Detection Guidance

This vulnerability is specific to the Linux kernel's net: shaper component and involves a race condition with VALID marking in XArray. Detection requires kernel-level inspection rather than network commands. Check kernel logs for net_shaper-related errors or warnings, particularly around XArray operations or UAF events. Use dmesg or journalctl to review kernel messages for anomalies in net_shaper functionality.

Impact Analysis

This vulnerability could allow an attacker to trigger a use-after-free condition in the Linux kernel's network shaper subsystem. This may lead to system crashes, privilege escalation, or arbitrary code execution, depending on the kernel's configuration and the attacker's capabilities.

Compliance Impact

This vulnerability affects compliance with standards like GDPR and HIPAA by potentially enabling a Use-After-Free (UAF) condition in the Linux kernel's network shaper component. This could lead to memory corruption, crashes, or unauthorized access, compromising data integrity and security. Such issues may violate requirements for secure data processing and protection in these regulations.

Mitigation Strategies

Apply the latest kernel patch that resolves this issue. Update your Linux kernel to a version containing the fix for the net: shaper VALID marking race condition. Monitor kernel security advisories for updates. If immediate patching is not possible, consider disabling the net_shaper module temporarily until the patch is applied.

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