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…
Does this matter?
Lower severity and a low EPSS score (0.13%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.13% probability · 3th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-476
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110Patch
- https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359aPatch
- https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5Patch
- https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000efPatch
- https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341fPatch
- https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810ePatch
- https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8Patch
- https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808Patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.