{"cve":"CVE-2026-23209","nvd":{"published":"2026-02-14T17:15:58.803","modified":"2026-10-19T19:17:41.920","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/11ba9f0dc865136174cb98834280fb21bbc950c7","https://git.kernel.org/stable/c/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a","https://git.kernel.org/stable/c/986967a162142710076782d5b93daab93a892980","https://git.kernel.org/stable/c/c43d0e787cbba569ec9d11579ed370b50fab6c9c","https://git.kernel.org/stable/c/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-23209","score":0.00176,"percentile":0.07126,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}