{"id":"CVE-2026-46086","state":"PUBLISHED","title":"net: bridge: use a stable FDB dst snapshot in RCU readers","description":"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 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.","publishedAt":"2026-05-27T12:58:28.137Z","updatedAt":"2026-10-15T01:20:24.801Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"c502fa9f094cb03d1d1685c71e2105ab359bc2b8","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"a6ae4511c07b91f597e461406c6330f0d4ff810e","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"0b9e4bbfb7c949151e3acd44ed4aa33614d2e110","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"81af4137a30c4c2dc694dea8cacb180bd66000ef","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"5424e678f9b304e148cf5dcc047cffc7a56a3bb5","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"9a2d9d4e657b23dc21f24cf139e3aeff0b61341f","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"df4601653201de21b487c3e7fffd464790cab808","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_arp_nd_proxy.c","net/bridge/br_fdb.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.14","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.140","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.86","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.27","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.4","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_arp_nd_proxy.c","net/bridge/br_fdb.c"]}],"references":["https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8","https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e","https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a","https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110","https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef","https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5","https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f","https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html","https://cert-portal.siemens.com/productcert/html/ssa-784472.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/46xxx/CVE-2026-46086.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46086","state":"PUBLISHED","datePublished":"2026-05-27T12:58:28.137Z","dateUpdated":"2026-10-15T01:20:24.801Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-13T15:03:33.096Z"},"containers":{"cna":{"title":"net: bridge: use a stable FDB dst snapshot in RCU readers","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"c502fa9f094cb03d1d1685c71e2105ab359bc2b8","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"a6ae4511c07b91f597e461406c6330f0d4ff810e","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"0b9e4bbfb7c949151e3acd44ed4aa33614d2e110","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"81af4137a30c4c2dc694dea8cacb180bd66000ef","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"5424e678f9b304e148cf5dcc047cffc7a56a3bb5","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"9a2d9d4e657b23dc21f24cf139e3aeff0b61341f","versionType":"git"},{"version":"960b589f86c74ce582922fcb996103271081f4de","status":"affected","lessThan":"df4601653201de21b487c3e7fffd464790cab808","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_arp_nd_proxy.c","net/bridge/br_fdb.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.14","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.140","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.86","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.27","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.4","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_arp_nd_proxy.c","net/bridge/br_fdb.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8"},{"url":"https://git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e"},{"url":"https://git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a"},{"url":"https://git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110"},{"url":"https://git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef"},{"url":"https://git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5"},{"url":"https://git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f"},{"url":"https://git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-06-19T11:59:23.674Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"5.10.259"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"6.6.140"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"6.12.86"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"6.18.27"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"7.0.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.14","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"affected":[{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 TM MFP - GNU/Linux subsystem","defaultStatus":"unknown","versions":[{"version":"0","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]}],"references":[{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html"}],"providerMetadata":{"shortName":"siemens-SADP","orgId":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","dateUpdated":"2026-10-15T01:20:24.801Z"},"x_adpType":"supplier"}]}}}