SB20260715110 - Red Hat Enterprise Linux 9 update for kernel
Published: July 15, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 5 vulnerabilities.
1) Use-after-free (CVE-ID: CVE-2026-43027)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in nf_conntrack_helper_unregister and expectation handling in netfilter nf_conntrack_helper when unregistering a helper while stale expectations remain. A local user can trigger helper unregistration and subsequent expectation access to cause a denial of service.
The issue is triggered because expectations referencing the helper survive cleanup and are later dereferenced during expectation dumps or packet-driven conntrack initialization.
2) Use-after-free (CVE-ID: CVE-2026-43499)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to use-after-free in remove_waiter() when rolling back a proxy lock from futex_requeue(). A local user can trigger the affected rtmutex slowlock and proxy-lock rollback path to cause a denial of service.
The issue can leave waiter task state uncleared and operate on the wrong top priority waiter task.
3) Use-after-free (CVE-ID: CVE-2026-46113)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in KVM shadow paging when handling guest page table changes between VM entries. A local user can modify guest page tables to create a stale reverse-mapping entry and trigger a stale rmap walk to cause a denial of service.
This can be triggered during operations such as dirty logging or MMU notifier invalidations.
4) NULL pointer dereference (CVE-ID: CVE-2026-53166)
CWE-ID: CWE-476 - NULL Pointer Dereference
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a NULL pointer dereference in remove_waiter() in the futex requeue logic when handling FUTEX_CMP_REQUEUE_PI operations that requeue a non-top waiter which already owns the target PI futex. A local user can trigger a self-deadlock condition to cause a denial of service.
5) Use-after-free (CVE-ID: CVE-2026-53359)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in the KVM x86 shadow paging logic when changing a PDE mapping from outside the guest and deleting a memslot. A local user can trigger stale rmap entries and subsequent dereference of a freed sptep to cause a denial of service.
The issue occurs when a modified PDE points to a non-leaf page, causing a role mismatch between reused shadow pages for large 2MB mappings and new 4KB mappings.
Remediation
Install update from vendor's website.