CVE-2026-46086

In the Linux kernel, the following vulnerability has been resolved: net: bridge: use a stable FDB dst snapshot in RCU readers Local FDB entries can be rewritten in place by `fdb_delete_local()`, which updates `f->dst` to another port or to `NULL` while keeping the entry alive. Several bridge RCU readers inspect `f->dst`, including `br_fdb_fillbuf()` through the `brforward_read()` sysfs path. These readers currently load `f->dst` multiple times and can therefore observe inconsistent values across the check and later dereference. In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change `f->dst` after the NULL check and before the `port_no` dereference, leading to a NULL-ptr-deref. Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()` with `WRITE_ONCE()` so the readers and writer use matching access patterns.

• linux linux kernel (>= 3.14.1 < 5.10.259) • linux linux kernel (>= 5.11 < 5.15.210) • linux linux kernel (>= 5.16 < 6.1.176) • linux linux kernel (>= 6.2 < 6.6.140) • linux linux kernel (>= 6.7 < 6.12.86) • linux linux kernel (>= 6.13 < 6.18.27) • linux linux kernel (>= 6.19 < 7.0.4) • linux linux kernel 3.14