Bug 2516928 (CVE-2026-74344)

Summary: CVE-2026-74344 kernel: bpf: Clear rb node linkage when freeing bpf_rb_root
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the BPF (Berkeley Packet Filter) subsystem of the Linux kernel. When freeing a BPF red-black tree root, the system could leave behind stale pointers in certain objects. If the memory address is reused, a subsequent operation could incorrectly access these stale pointers, leading to memory corruption. This issue could potentially cause system instability or a denial of service.
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Description OSIDB Bzimport 2026-08-15 06:40:50 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Clear rb node linkage when freeing bpf_rb_root

bpf_rb_root_free() detaches the root by copying the current rb_root_cached
and then replacing the live root with RB_ROOT_CACHED. It then walks the
copied root and drops each object contained in the tree.

This leaves the rb node state intact while dropping the object. If the
object is refcounted and survives the drop, its bpf_rb_node_kern still
contains an owner pointer to the freed root and stale rb tree linkage. If
a later bpf_rb_root allocation reuses the same address, bpf_rbtree_remove()
can incorrectly pass the owner check and call rb_erase_cached() on a node
whose rb pointers belong to the old tree.

Mirror the list draining behavior by marking nodes as busy while the root
is being detached, then clear the rb node and release the owner before
dropping the containing object. This makes surviving nodes unowned and
safe to reject from remove or accept for a later add.
Comment 1 Keith Grant 2026-08-20 18:16:04 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081558-CVE-2026-74344-0bdd@gregkh/T