CVE-2026-46086
Last modified
CVE-2026-46086 is a medium-severity vulnerability rated 5.5/10 on the CVSS scale. 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. EPSS estimates a 0.12% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| 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 |
References
Timeline
- Published
- Last Modified
- Status
- Undergoing Analysis
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How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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