CVE-2026-89747
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In the Linux kernel, writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page. trace_pipe readers hold pointers into those pages, and ring_buffer_peek() returns the event pointer after dropping the lock, so changing the sub-buffer order in that window leads to a use-after-free.
Risk Assessment
A use-after-free in the tracing mechanism could be exploited for privilege escalation or cause a kernel crash. In environments with active tracing and the ability to change sub-buffer size, the risk is significant.
Recommendation
Update the Linux kernel to a version with the fix that wraps the order change with trace_access_lock(RING_BUFFER_ALL_CPUS). Restrict write access to buffer_subbuf_size_kb to trusted users.
Other vulnerabilities in Linux kernel
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- CVE-2026-100071Unknown
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- CVE-2026-100070Unknown
In the Linux kernel, a bug in the netfilter nf_nat_sip module was fixed where the offset was not rewound when NAT shrinks the packet. If map_addr() changes the packet length, coff may point to an incorrect position, potentially causing subsequent Contact headers to be skipped and leaking internal network details.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS