High [CVE-2026-74496] Fix use-after-free in fou_create
This high-severity Red Hat Linux advisory covers CVE-2026-74496 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
In the Linux kernel, the following vulnerability has been resolved: fou: Fix use-after-free in fou_create() fou_create() publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data.
A concurrent receive can then dereference the freed object in fou_from_sock(). This ordering issue was previously noted in the linked discussion.
The failure is reachable when local port 0 is requested. Each socket binds to a different ephemeral port, but fou_cfg_cmp() compares the requested port 0 and reports -EALREADY once an entry already exists.
Release the tunnel socket before freeing fou so sk_user_data is cleared first, and defer reclamation with kfree_rcu() to protect concurrent RCU readers. This matches the lifetime handling in fou_release().
A flaw was found in the Linux kernel's Foo Over UDP (FOU) tunnel driver. An ordering issue in the `fou_create()` function can lead to a use-after-free vulnerability.
This occurs when a `struct fou` object is published before being fully added to the system's list. If the addition fails, the object can be freed while still accessible, allowing a concurrent operation to access the freed memory.
This could result in memory corruption and potentially lead to system instability or a denial of service.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 47 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 47 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 47 minutes ago·verify at source
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