{"id":"CVE-2026-46086","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: use a stable FDB dst snapshot in RCU readers\n\nLocal FDB entries can be rewritten in place by `fdb_delete_local()`, which\nupdates `f->dst` to another port o…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: use a stable FDB dst snapshot in RCU readers\n\nLocal FDB entries can be rewritten in place by `fdb_delete_local()`, which\nupdates `f->dst` to another port o…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-476"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 3.14.1, < 5.10.259","linux_kernel >= 5.11, < 5.15.210","linux_kernel >= 5.16, < 6.1.176","linux_kernel >= 6.2, < 6.6.140","linux_kernel >= 6.7, < 6.12.86","linux_kernel >= 6.13, < 6.18.27","linux_kernel >= 6.19, < 7.0.4","linux_kernel = 3.14"],"patched":["linux_kernel 7.0.4"],"published":"2026-05-27","updated":"2026-09-08","sourceUpdated":"2026-09-08T09:18:07.390","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-46086","references":[{"url":"https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00125,"epssPercentile":0.0257,"ingestedAt":"2026-09-08T13:33:24.435Z","slug":"CVE-2026-46086","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: use a stable FDB dst snapshot in RCU readers\n\nLocal FDB entries can be rewritten in place by `fdb_delete_local()`, which\nupdates `f->dst` to another port or to `NULL` while keeping the entry\nalive. Several bridge RCU readers inspect `f->dst`, including\n`br_fdb_fillbuf()` through the `brforward_read()` sysfs path.\n\nThese readers currently load `f->dst` multiple times and can therefore\nobserve inconsistent values across the check and later dereference.\nIn `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change\n`f->dst` after the NULL check and before the `port_no` dereference,\nleading to a NULL-ptr-deref.\n\nFix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each\naffected RCU reader and using that snapshot for the rest of the access\nsequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()`\nwith `WRITE_ONCE()` so the readers and writer use matching access patterns.\n\n## Affected\n\n- `linux_kernel >= 3.14.1, < 5.10.259`\n- `linux_kernel >= 5.11, < 5.15.210`\n- `linux_kernel >= 5.16, < 6.1.176`\n- `linux_kernel >= 6.2, < 6.6.140`\n- `linux_kernel >= 6.7, < 6.12.86`\n- `linux_kernel >= 6.13, < 6.18.27`\n- `linux_kernel >= 6.19, < 7.0.4`\n- `linux_kernel = 3.14`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.0.4`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}