{"id":"CVE-2026-23209","title":"macvlan: fix error recovery in macvlan_common_newlink()","summary":"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…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < da5c6b8ae47e414be47e5e04def15b25d5c962dc","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < c43d0e787cbba569ec9d11579ed370b50fab6c9c","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 11ba9f0dc865136174cb98834280fb21bbc950c7","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 986967a162142710076782d5b93daab93a892980","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66","Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < f8db6475a83649689c087a8f52486fcc53e627e9","Linux 4.9"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-06-16T20:31:00.910619Z"},"published":"2026-02-14","updated":"2026-10-19","sourceUpdated":"2026-10-19T18:35:38.702Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23209","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"}],"tags":["cve.org"],"epss":0.0014,"epssPercentile":0.02994,"ingestedAt":"2026-10-19T19:38:06.501Z","slug":"CVE-2026-23209","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < da5c6b8ae47e414be47e5e04def15b25d5c962dc`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < c43d0e787cbba569ec9d11579ed370b50fab6c9c`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 11ba9f0dc865136174cb98834280fb21bbc950c7`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 986967a162142710076782d5b93daab93a892980`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66`\n- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < f8db6475a83649689c087a8f52486fcc53e627e9`\n- `Linux 4.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}