{"id":"CVE-2026-23209","state":"PUBLISHED","title":"macvlan: fix error recovery in macvlan_common_newlink()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: fix error recovery in macvlan_common_newlink()\n\nvalis provided a nice repro to crash the kernel:\n\nip link add p1 type veth peer p2\nip link set address 00:00:00:00:00:20 dev p1\nip link set up dev p1\nip link set up dev p2\n\nip link add mv0 link p2 type macvlan mode source\nip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20\n\nping -c1 -I p1 1.2.3.4\n\nHe also gave a very detailed analysis:\n\n<quote valis>\n\nThe issue is triggered when a new macvlan link is created  with\nMACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or\nMACVLAN_MACADDR_SET) parameter, lower device already has a macvlan\nport and register_netdevice() called from macvlan_common_newlink()\nfails (e.g. because of the invalid link name).\n\nIn this case macvlan_hash_add_source is called from\nmacvlan_change_sources() / macvlan_common_newlink():\n\nThis adds a reference to vlan to the port's vlan_source_hash using\nmacvlan_source_entry.\n\nvlan is a pointer to the priv data of the link that is being created.\n\nWhen register_netdevice() fails, the error is returned from\nmacvlan_newlink() to rtnl_newlink_create():\n\n        if (ops->newlink)\n                err = ops->newlink(dev, &params, extack);\n        else\n                err = register_netdevice(dev);\n        if (err < 0) {\n                free_netdev(dev);\n                goto out;\n        }\n\nand free_netdev() is called, causing a kvfree() on the struct\nnet_device that is still referenced in the source entry attached to\nthe lower device's macvlan port.\n\nNow all packets sent on the macvlan port with a matching source mac\naddress will trigger a use-after-free in macvlan_forward_source().\n\n</quote valis>\n\nWith all that, my fix is to make sure we call macvlan_flush_sources()\nregardless of @create value whenever \"goto destroy_macvlan_port;\"\npath is taken.\n\nMany thanks to valis for following up on this issue.","publishedAt":"2026-02-14T16:27:31.175Z","updatedAt":"2026-10-19T18:35:38.702Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"da5c6b8ae47e414be47e5e04def15b25d5c962dc","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"c43d0e787cbba569ec9d11579ed370b50fab6c9c","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"11ba9f0dc865136174cb98834280fb21bbc950c7","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"986967a162142710076782d5b93daab93a892980","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"f8db6475a83649689c087a8f52486fcc53e627e9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/macvlan.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.9","versionType":"semver"},{"version":"5.10.250","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.200","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.163","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.124","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.70","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.10","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/macvlan.c"]}],"references":["https://git.kernel.org/stable/c/da5c6b8ae47e414be47e5e04def15b25d5c962dc","https://git.kernel.org/stable/c/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a","https://git.kernel.org/stable/c/c43d0e787cbba569ec9d11579ed370b50fab6c9c","https://git.kernel.org/stable/c/11ba9f0dc865136174cb98834280fb21bbc950c7","https://git.kernel.org/stable/c/986967a162142710076782d5b93daab93a892980","https://git.kernel.org/stable/c/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66","https://git.kernel.org/stable/c/f8db6475a83649689c087a8f52486fcc53e627e9"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23209.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23209","state":"PUBLISHED","datePublished":"2026-02-14T16:27:31.175Z","dateUpdated":"2026-10-19T18:35:38.702Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:45.986Z"},"containers":{"cna":{"title":"macvlan: fix error recovery in macvlan_common_newlink()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: fix error recovery in macvlan_common_newlink()\n\nvalis provided a nice repro to crash the kernel:\n\nip link add p1 type veth peer p2\nip link set address 00:00:00:00:00:20 dev p1\nip link set up dev p1\nip link set up dev p2\n\nip link add mv0 link p2 type macvlan mode source\nip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20\n\nping -c1 -I p1 1.2.3.4\n\nHe also gave a very detailed analysis:\n\n<quote valis>\n\nThe issue is triggered when a new macvlan link is created  with\nMACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or\nMACVLAN_MACADDR_SET) parameter, lower device already has a macvlan\nport and register_netdevice() called from macvlan_common_newlink()\nfails (e.g. because of the invalid link name).\n\nIn this case macvlan_hash_add_source is called from\nmacvlan_change_sources() / macvlan_common_newlink():\n\nThis adds a reference to vlan to the port's vlan_source_hash using\nmacvlan_source_entry.\n\nvlan is a pointer to the priv data of the link that is being created.\n\nWhen register_netdevice() fails, the error is returned from\nmacvlan_newlink() to rtnl_newlink_create():\n\n        if (ops->newlink)\n                err = ops->newlink(dev, &params, extack);\n        else\n                err = register_netdevice(dev);\n        if (err < 0) {\n                free_netdev(dev);\n                goto out;\n        }\n\nand free_netdev() is called, causing a kvfree() on the struct\nnet_device that is still referenced in the source entry attached to\nthe lower device's macvlan port.\n\nNow all packets sent on the macvlan port with a matching source mac\naddress will trigger a use-after-free in macvlan_forward_source().\n\n</quote valis>\n\nWith all that, my fix is to make sure we call macvlan_flush_sources()\nregardless of @create value whenever \"goto destroy_macvlan_port;\"\npath is taken.\n\nMany thanks to valis for following up on this issue."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"da5c6b8ae47e414be47e5e04def15b25d5c962dc","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"c43d0e787cbba569ec9d11579ed370b50fab6c9c","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"11ba9f0dc865136174cb98834280fb21bbc950c7","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"986967a162142710076782d5b93daab93a892980","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66","versionType":"git"},{"version":"aa5fd0fb77486b8a6764ead8627baa14790e4280","status":"affected","lessThan":"f8db6475a83649689c087a8f52486fcc53e627e9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/macvlan.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.9","versionType":"semver"},{"version":"5.10.250","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.200","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.163","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.124","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.70","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.10","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/macvlan.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/da5c6b8ae47e414be47e5e04def15b25d5c962dc"},{"url":"https://git.kernel.org/stable/c/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a"},{"url":"https://git.kernel.org/stable/c/c43d0e787cbba569ec9d11579ed370b50fab6c9c"},{"url":"https://git.kernel.org/stable/c/11ba9f0dc865136174cb98834280fb21bbc950c7"},{"url":"https://git.kernel.org/stable/c/986967a162142710076782d5b93daab93a892980"},{"url":"https://git.kernel.org/stable/c/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66"},{"url":"https://git.kernel.org/stable/c/f8db6475a83649689c087a8f52486fcc53e627e9"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Triggering the vulnerability requires CAP_NET_ADMIN to create macvlan interfaces, which is reachable via user namespaces (unshare -Urn) by an unprivileged local user. The setup is local even though the UAF is triggered by network packets.\nAC:L - The vulnerability is deterministically triggered by a straightforward sequence: create a macvlan source with a known-bad interface name to cause register_netdevice() failure, then send a packet with the matching source MAC. No race condition or special conditions needed.\nPR:L - Requires CAP_NET_ADMIN for RTM_NEWLINK netlink operations, but this capability is obtainable by any unprivileged user through user namespaces (unshare -Urn), as netlink_net_capable checks against the network namespace's user_ns, not init_user_ns.\nUI:N - No user interaction is needed. The attacker sets up the vulnerable macvlan configuration and triggers the UAF by sending packets on the lower device, all without any victim action.\nS:U - The vulnerability operates within the kernel's security context. While it allows kernel code execution, it does not cross a virtualization or sandbox boundary — it is standard kernel privilege escalation.\nC:H - The use-after-free in macvlan_forward_source() dereferences a freed macvlan_dev structure. An attacker can reclaim the freed memory via heap spraying, enabling arbitrary kernel memory reads through controlled object contents.\nI:H - The UAF accesses and writes to the freed macvlan_dev structure (e.g., macvlan_count_rx updates statistics). With heap spraying to reclaim the freed object, this provides arbitrary write primitives that can be leveraged for code execution.\nA:H - The use-after-free causes dereferencing of freed memory, which reliably causes kernel crashes (oops/panic) when the freed memory is reclaimed for other purposes. The reproducer in the commit message demonstrates a reliable crash."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:20:40.203Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.10.250"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.15.200"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.1.163"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.6.124"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.12.70"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.18.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.19"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23209","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-06-16T20:31:00.910619Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:38.702Z"}}]}}}