CVE-2026-74288

Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source

AV:LAttack vector, local

The bug is reached only through local kernel networking control paths: fib_rules_dump() runs during register_fib_notifier() and races with RTM_DELRULE netlink handling in fib_delrule(), not via remotely received packets or a network-facing protocol handler.

AC:LAttack complexity, low

Exploitation is a race where the attacker concurrently deletes FIB rules (repeated RTM_DELRULE or netns teardown) while fib_rules_dump() replays RULE_ADD events; the attacker controls both sides and can retry, as demonstrated by syzbot during netdevsim reload/cleanup_net.

PR:LPrivileges required, low

Triggering concurrent FIB rule deletion requires CAP_NET_ADMIN on the target network namespace, which unprivileged users can obtain inside user/network namespaces (e.g., unshare -Urn), while driver registration commonly occurs in the same namespace during netdevsim/devlink setup.

UI:NUser interaction, none

No end-user or administrator UI action is required beyond programmatic netlink/devlink operations that an attacker can script; exploitation does not depend on a victim opening files, clicking links, or mounting filesystems.

S:UScope, unchanged

Impact is a kernel heap use-after-free in fib_rule handling leading to memory corruption within the host kernel; it does not inherently cross a VM/hypervisor or IOMMU security boundary without separate exploitation of unrelated boundaries.

C:HConfidentiality impact, high

A dying fib_rule can be passed to FIB notifiers after its refcount hits zero; handlers such as rocker_router_fib_event() call fib_rule_get() and later dereference rule fields in workqueues, enabling reads of freed slab memory and potential kernel pointer disclosure.

I:HIntegrity impact, high

The UAF hands attackers control over the lifetime and contents of freed fib_rule objects; with heap grooming this class of corruption is reasonably leveraged into arbitrary kernel writes or control-flow hijack, not merely a benign warning.

A:HAvailability impact, high

refcount_inc() on a zero refcount emits use-after-free warnings and concurrent dereference of freed fib_rule structures during dump/replay can cause kernel oops/panics, especially under automated stress seen in syzbot reproductions.