CVE-2026-99163 tracing/histograms: Reject non-stacktrace fields for synthetic stacktrace fields
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99163?
CVE-2026-99163 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tracing/histograms: Reject non-stacktrace fields for synthetic stacktrace fields
In check_synth_field(), when a synthetic event field is a stacktrace (field->is_stack) and the histogram field is not a "long[" stacktrace array, validation falls through to the generic size and signedness comparison.
Because parse_synth_field() sets a stacktrace field's type to "__data_loc unsigned long[]", its size is sizeof(u64) and synth_field_signed() marks it as signed. Consequently, any 8-byte signed scalar histogram field passes the fallback check, and its scalar value is subsequently dereferenced as a kernel stacktrace pointer in get_field_size() and trace_stack().
Furthermore, checking strstr(hist_field->type, "long[") is insufficient because tracepoint fields defined with __bitmask() or __rel_bitmask() also have type "__data_loc unsigned long[]" or "__rel_loc unsigned long[]", whilst create_hist_field() treats them as 4-byte scalar values without HIST_FIELD_FL_STACKTRACE.
Propagate HIST_FIELD_FL_STACKTRACE to variable references and field variables (whilst excluding variable aliases from per-element stacktrace capture), and reject any mismatch between HIST_FIELD_FL_STACKTRACE and field->is_stack in check_synth_field().
Which versions are affected by CVE-2026-99163?
How do I fix CVE-2026-99163?
Upgrade to a fixed version.
Is CVE-2026-99163 being exploited?
There is no known exploitation of CVE-2026-99163 in the wild and no public exploit code.
Sources
Also known as AZL-111305, BELL-CVE-2026-99163, DEBIAN-CVE-2026-99163, GHSA-8cf9-783r-h9xg, UBUNTU-CVE-2026-99163.