{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23209", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.986Z", "datePublished": "2026-02-14T16:27:31.175Z", "dateUpdated": "2026-08-05T12:20:40.203Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:20:40.203Z" }, "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\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, ¶ms, 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\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." } ], "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/macvlan.c" ], "versions": [ { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "da5c6b8ae47e414be47e5e04def15b25d5c962dc", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "c43d0e787cbba569ec9d11579ed370b50fab6c9c", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "11ba9f0dc865136174cb98834280fb21bbc950c7", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "986967a162142710076782d5b93daab93a892980", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66", "status": "affected", "versionType": "git" }, { "version": "aa5fd0fb77486b8a6764ead8627baa14790e4280", "lessThan": "f8db6475a83649689c087a8f52486fcc53e627e9", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/macvlan.c" ], "versions": [ { "version": "4.9", "status": "affected" }, { "version": "0", "lessThan": "4.9", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.250", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.200", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.163", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.124", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.70", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.10", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "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" } ] } ] } ], "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" } ], "title": "macvlan: fix error recovery in macvlan_common_newlink()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-06-16T20:31:00.910619Z", "id": "CVE-2026-23209", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-06-16T20:31:11.304Z" } } ] } }