Tracker / CVE-2026-46086
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.
Affected products and versions
| linux | linux_kernel |
|---|---|
| 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 · 6.13 → 6.18.27 |
| linux | linux_kernel · 6.19 → 7.0.4 |
| linux | linux_kernel · 6.2 → 6.6.140 |
| linux | linux_kernel · 6.7 → 6.12.86 |