CVE-2026-99159

Published Oct 28, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix the sub-buffer array base in rb_meta_subbuf_idx() On a persistent ring buffer, rb_meta_subbuf_idx() can return an index one sub-buffer too high. rb_setup_ids_meta_page() then fills subbuf_ids[] shifted by one and leaves subbuf_ids[0] NULL, which __rb_map_vma() dereferences when userspace maps trace_pipe_raw. rb_update_meta_reader() writes two such indices into meta->buffers[], which rb_cpu_meta_valid() would reject on the next boot, discarding the previous boot's trace. A CPU's sub-buffer array starts after its meta header and the nr_subbufs integers that follow, aligned up to a sub-buffer. rb_meta_subbuf_idx() inverts that calculation but skips only the integers, not the header, so its base is one sub-buffer low whenever the omitted header size crosses the alignment boundary. Invert the calculation with rb_subbufs_from_meta() rather than repeating it. rb_range_buffer() maps an index back to an address through the same helper, so the two directions can no longer disagree.

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References

Frequently Asked Questions

What is CVE-2026-99159? +
In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix the sub-buffer array base in rb_meta_subbuf_idx() On a persistent ring buffer, rb_meta_subbuf_idx() can return an index one sub-buffer too high. rb_setup_ids_meta_page() then fills subbuf_ids[] shifted by one and leaves subbuf_ids[0] NULL, which __rb_map_vma() dereferences when userspace maps trace_pipe_raw. rb_update_meta_reader() writes two such indices into meta->buffers[], which rb_cpu_meta_valid() would reject on the next boot, discarding the previous boot's trace. A CPU's sub-buffer array starts after its meta header and the nr_subbufs integers that follow, aligned up to a sub-buffer. rb_meta_subbuf_idx() inverts that calculation but skips only the integers, not the header, so its base is one sub-buffer low whenever the omitted header size crosses the alignment boundary. Invert the calculation with rb_subbufs_from_meta() rather than repeating it. rb_range_buffer() maps an index back to an address through the same helper, so the two directions can no longer disagree.
How do I check if I'm vulnerable to CVE-2026-99159? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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