{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-43249", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-43249" ], "published": "2026-05-06T11:29:17Z", "summary": "9p/xen: protect xen_9pfs_front_free against concurrent calls", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p/xen: protect xen_9pfs_front_free against concurrent calls\n\nThe xenwatch thread can race with other back-end change notifications\nand call xen_9pfs_front_free() twice, hitting the observed general\nprotection fault due to a double-free. Guard the teardown path so only\none caller can release the front-end state at a time, preventing the\ncrash.\n\nThis is a fix for the following double-free:\n\n[ 27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI\n[ 27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none)\n[ 27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150\n[ 27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 <48> 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42\n[ 27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246\n[ 27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000\n[ 27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000\n[ 27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000\n[ 27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68\n[ 27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040\n[ 27.052404] FS: 0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000\n[ 27.052408] CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660\n[ 27.052418] Call Trace:\n[ 27.052420] \n[ 27.052422] xen_9pfs_front_changed+0x5d5/0x720\n[ 27.052426] ? xenbus_otherend_changed+0x72/0x140\n[ 27.052430] ? __pfx_xenwatch_thread+0x10/0x10\n[ 27.052434] xenwatch_thread+0x94/0x1c0\n[ 27.052438] ? __pfx_autoremove_wake_function+0x10/0x10\n[ 27.052442] kthread+0xf8/0x240\n[ 27.052445] ? __pfx_kthread+0x10/0x10\n[ 27.052449] ? __pfx_kthread+0x10/0x10\n[ 27.052452] ret_from_fork+0x16b/0x1a0\n[ 27.052456] ? __pfx_kthread+0x10/0x10\n[ 27.052459] ret_from_fork_asm+0x1a/0x30\n[ 27.052463] \n[ 27.052465] Modules linked in:\n[ 27.052471] ---[ end trace 0000000000000000 ]---", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null, "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-43249" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/a5d00dff97118a32fcf5fec7a4c3f864c4620c4e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/59e7707492576bdbfa8c1dbe7d90791df31e4773" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/bf841d43f7a33d75675ba7f4e214ac1c67913065" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ce8ded2e61f47747e31eeefb44dc24a2160a7e32" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 8.8, "cvss_v3_severity": "High", "scenario": "AV:A - The vulnerable 9p Xen frontend is reached through Xenbus/backend state changes from a paired Xen backend or service domain on the same host/logical I/O fabric. It is not directly routable over IP, but it is reachable across an adjacent inter-domain channel.\nAC:L - A malicious backend can repeatedly queue the state transitions/removal paths that lead to concurrent or repeated xen_9pfs_front_free() calls. The trigger does not depend on conditions outside the attacker-controlled backend notification sequence.\nPR:N - No privileges in the vulnerable guest are required; the guest frontend accepts the triggering state changes from its configured backend via Xenstore. Control of the backend is the attack position rather than a credential inside the target Linux kernel.\nUI:N - No victim user action is needed after the Xen 9pfs frontend device is present and bound. Backend state changes are processed asynchronously by xenwatch.\nS:U - The corrupted objects and resulting crash/code-execution risk are within the same guest Linux kernel running the vulnerable frontend. The issue does not demonstrate a guest-to-host or hypervisor escape.\nC:H - This is kernel heap memory corruption via double-free of frontend state and associated ring resources. Such corruption can plausibly be shaped into use-after-free/freelist manipulation and arbitrary kernel memory disclosure, so the higher impact is warranted.\nI:H - The double-free can corrupt kernel allocator metadata or free a reallocated object, giving a plausible path to arbitrary write or control-flow compromise. Under the required uncertainty rule, this is scored as high integrity impact.\nA:H - The reported failure is a general protection fault in xenwatch from dereferencing poisoned freed memory. A malicious backend can crash the guest kernel, causing high availability impact." } } }