CVE-2026-74750
Received Received - Intake

Kernel Key Slot Release Use-After-Free in OpenVPN

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ovpn: defer key slot crypto freeing to workqueue Key slots are released through a kref and the existing release path frees the AEAD transforms from an RCU callback. That is not safe for all crypto implementations: crypto_free_aead can sleep, for example when an async or hardware implementation has teardown work to complete. Use queue_rcu_work for key-slot release. This keeps the RCU grace period needed by lockless key-slot readers, but runs the actual crypto teardown from workqueue context where sleeping is allowed. Once the rcu_work callback runs, pre-existing RCU readers are gone, and the final kref put already proves that no transform user remains, so the worker can release the AEAD transforms and free the slot directly. The previous patch drains ovpn_wq during module exit, so queued key-slot teardown work cannot outlive module text.

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-74750
EUVD
EUVD-2026-66580

Affected Vendors & Products

Currently, no data is known.

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves unsafe freeing of cryptographic key slots in the OpenVPN (ovpn) module. The issue occurs because crypto_free_aead can sleep, but the current implementation uses an RCU callback to free AEAD transforms, which is not safe for all crypto implementations. The fix uses queue_rcu_work to defer key slot crypto freeing to a workqueue, allowing sleeping operations to complete safely while maintaining RCU grace periods for lockless readers.

Detection Guidance

This vulnerability is specific to the Linux kernel's OpenVPN implementation and requires kernel-level inspection. Detection involves checking the kernel version and OpenVPN module for the affected code path. Use commands like 'uname -a' to check kernel version and 'lsmod | grep ovpn' to verify if the OpenVPN module is loaded.

Impact Analysis

This vulnerability could lead to system instability or crashes if the kernel attempts to free cryptographic resources in an unsafe context. It may cause unexpected behavior in OpenVPN or other applications relying on the affected crypto operations, potentially resulting in denial of service or data corruption.

Mitigation Strategies

Update the Linux kernel to a patched version that includes the fix for this vulnerability. Monitor distributions for kernel updates addressing CVE-2026-74750. If using OpenVPN, ensure the module is updated or recompiled with the fix.

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