Medium [CVE-2026-74395] Fix devx subscribe-event unwind NULL dereference
This medium-severity Red Hat Linux advisory covers CVE-2026-74395 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
In the Linux kernel, the following vulnerability has been resolved: RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT() links event_sub into sub_list before initializing the fields used by the shared error path.
If eventfd_ctx_fdget() then fails, the unwind path dereferences event_sub->ev_file in uverbs_uobject_put() and calls subscribe_event_xa_dealloc() with an unset xa_key_level1. subscribe_event_xa_alloc() creates the XA entry exactly once for a given key_level1, on the first occurrence of that key.
Enforce that by adding devx_key_in_sub_list() and calling subscribe_event_xa_dealloc() only when the last matching pending entry is being cleaned up. During the `devx subscribe-event` unwind process, a null pointer dereference can occur if `eventfd_ctx_fdget()` fails.
This issue arises because `event_sub` is linked into `sub_list` before its fields are properly initialized, leading to an attempt to dereference a null pointer. A local attacker could potentially exploit this to cause a denial of service (DoS) by crashing the system.
Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-476.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.
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 57 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 57 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 57 minutes ago·verify at source
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