CVE-2026-89748

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

Reached only via local tracefs reads of remotes/*/trace_pipe or remotes/*/trace, which call ring_buffer_consume/peek -> __rb_get_reader_page_from_remote() -> swap_reader_page() into simple_ring_buffer_swap_reader_page() (ARM64 nVHE hyp tracing or the TRACE_REMOTE_TEST module). No network, adjacent-radio, or physical path exists.

AC:LAttack complexity, low

An attacker with tracefs access shrinks remotes/*/buffer_size_kb, enables tracing, and storms events via remotes/*/write_event or KVM hyp events while reading trace_pipe. That drives the writer to move the head across the eight cmpxchg retries; the attacker controls both sides and can retry until inverted exhaustion hits.

PR:LPrivileges required, low

remotes/ files are mode 0440/0640 and use custom fops with no capable() or tracing_check_open_get_tr() check, only DAC. tracing-gid mounts on Android eng/Perfetto, ChromeOS, and developer kernels grant this to unprivileged tracing-group users, matching CVE-2026-89499 and prior CNA tracefs scores.

UI:NUser interaction, none

The attacker opens, configures, and reads their own remotes/*/trace_pipe and related tracefs files. No separate victim mount, click, or other user action is required.

S:UScope, unchanged

Corruption is of host kernel ring-buffer buffer_page lists and simple_ring_buffer metadata in the same OS security authority. A host-local tracefs user cannot use this as a VM, IOMMU, or guest-to-host escape.

C:HConfidentiality impact, high

Inverted retry exhaustion leaves the reader page in the writer ring (success reported as error) or makes the host adopt a live writer page as reader (failure reported as success). Concurrent commits tear event headers so rb_event_length() returns unbounded sizes, and later peeks follow corrupted buffer_page pointers, enabling out-of-bounds kernel reads.

I:HIntegrity impact, high

After a failed final cmpxchg the function still updates head_page, reader_page, link.prev, and meta.reader.id, and the host splices buffer_page lists as if the swap succeeded. That kernel list-metadata corruption is exploitable for arbitrary writes and control-flow hijack, matching sibling remote-swap CVE-2026-89499.

A:HAvailability impact, high

The inverted path hits WARN_ON_ONCE(prev_reader == new_reader) on the host, can infinite-spin in simple_rb_find_head() on SIMPLE_RB_LINK_HEAD_MOVING, and oopses on corrupted page pointers. panic_on_warn turns those WARNs into panics, and the attacker can retrigger the path at will.