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CVE-2026-46086 In the Linux kernel, the following vulnerability has been resolved: net: bridge: use a stable FDB dst snapshot in RCU…

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.

Affected products and versions

Product Affected versions Fixed in
Linux 7.1 earliest → < 7.1 7.1
Linux 7.0 earliest → < 7.0.4 7.0.4
Linux 6.18 earliest → < 6.18.27 6.18.27
Linux 6.12 earliest → < 6.12.86 6.12.86
Linux 6.6 earliest → < 6.6.140 6.6.140
Linux 6.1 earliest → < 6.1.176 6.1.176
Linux 5.15 earliest → < 5.15.210 5.15.210
Linux 5.10 earliest → < 5.10.259 5.10.259
Linux 3.14 No fix stated
Show the 4 other branches
Product Affected versions Fixed in
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Versions not published

References

Timeline

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