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CVE-2026-46086

net: bridge: use a stable FDB dst snapshot in RCU readers

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.140, 6.12.86, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 960b589f86c74ce582922fcb996103271081f4de · fixed in c502fa9f094cb03d1d1685c71e2105ab359bc2b8; From 960b589f86c74ce582922fcb996103271081f4de · fixed in a6ae4511c07b91f597e461406c6330f0d4ff810e; From 960b589f86c74ce582922fcb996103271081f4de · fixed in 1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a; From 960b589f86c74ce582922fcb996103271081f4de · fixed in 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110; From 960b589f86c74ce582922fcb996103271081f4de · fixed in 81af4137a30c4c2dc694dea8cacb180bd66000ef; From 960b589f86c74ce582922fcb996103271081f4de · fixed in 5424e678f9b304e148cf5dcc047cffc7a56a3bb5; From 960b589f86c74ce582922fcb996103271081f4de · fixed in 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f; From 960b589f86c74ce582922fcb996103271081f4de · fixed in df4601653201de21b487c3e7fffd464790cab808

  • Linux Linux

    3.14

  • KernelLinux

    From 3.14.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.140; From 6.7.0 · fixed in 6.12.86; From 6.13.0 · fixed in 6.18.27; From 6.19.0 · fixed in 7.0.4

References 8

git.kernel.org