High [CVE-2026-72218] Plug nlm_file refcount leak on cached nlm_do_fopen failure
This high-severity Red Hat Linux advisory covers CVE-2026-72218 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: lockd: Plug nlm_file refcount leak on cached nlm_do_fopen() failure The cached-file path in nlm_lookup_file() reaches the found: label unconditionally, even when nlm_do_fopen() fails. At that label *result and file->f_count are updated before the error is returned.
The wrappers nlm3svc_lookup_file() and nlm4svc_lookup_file() then bail out of their switch without copying *result back to their caller, so the proc handler's local nlm_file pointer remains NULL and the cleanup path skips nlm_release_file().
The f_count increment is never released, and nlm_traverse_files() can no longer reap the file because its refcount never returns to zero between requests. Short-circuit the cached path so neither *result nor f_count is touched when nlm_do_fopen() fails on a hashed nlm_file.
This prevents the file's reference count from returning to zero, causing a resource leak. Over time, this can lead to resource exhaustion and a Denial of Service (DoS) condition.
Red Hat severity: Moderate — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-772.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: kernel-rt.
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 23 days 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 23 days 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 23 days ago·verify at source
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