{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23294", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.993Z", "datePublished": "2026-03-25T10:26:51.946Z", "dateUpdated": "2026-08-05T12:21:10.341Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:21:10.341Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix race in devmap on PREEMPT_RT\n\nOn PREEMPT_RT kernels, the per-CPU xdp_dev_bulk_queue (bq) can be\naccessed concurrently by multiple preemptible tasks on the same CPU.\n\nThe original code assumes bq_enqueue() and __dev_flush() run atomically\nwith respect to each other on the same CPU, relying on\nlocal_bh_disable() to prevent preemption. However, on PREEMPT_RT,\nlocal_bh_disable() only calls migrate_disable() (when\nPREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable\npreemption, which allows CFS scheduling to preempt a task during\nbq_xmit_all(), enabling another task on the same CPU to enter\nbq_enqueue() and operate on the same per-CPU bq concurrently.\n\nThis leads to several races:\n\n1. Double-free / use-after-free on bq->q[]: bq_xmit_all() snapshots\n cnt = bq->count, then iterates bq->q[0..cnt-1] to transmit frames.\n If preempted after the snapshot, a second task can call bq_enqueue()\n -> bq_xmit_all() on the same bq, transmitting (and freeing) the\n same frames. When the first task resumes, it operates on stale\n pointers in bq->q[], causing use-after-free.\n\n2. bq->count and bq->q[] corruption: concurrent bq_enqueue() modifying\n bq->count and bq->q[] while bq_xmit_all() is reading them.\n\n3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq->dev_rx and\n bq->xdp_prog after bq_xmit_all(). If preempted between\n bq_xmit_all() return and bq->dev_rx = NULL, a preempting\n bq_enqueue() sees dev_rx still set (non-NULL), skips adding bq to\n the flush_list, and enqueues a frame. When __dev_flush() resumes,\n it clears dev_rx and removes bq from the flush_list, orphaning the\n newly enqueued frame.\n\n4. __list_del_clearprev() on flush_node: similar to the cpumap race,\n both tasks can call __list_del_clearprev() on the same flush_node,\n the second dereferences the prev pointer already set to NULL.\n\nThe race between task A (__dev_flush -> bq_xmit_all) and task B\n(bq_enqueue -> bq_xmit_all) on the same CPU:\n\n Task A (xdp_do_flush) Task B (ndo_xdp_xmit redirect)\n ---------------------- --------------------------------\n __dev_flush(flush_list)\n bq_xmit_all(bq)\n cnt = bq->count /* e.g. 16 */\n /* start iterating bq->q[] */\n <-- CFS preempts Task A -->\n bq_enqueue(dev, xdpf)\n bq->count == DEV_MAP_BULK_SIZE\n bq_xmit_all(bq, 0)\n cnt = bq->count /* same 16! */\n ndo_xdp_xmit(bq->q[])\n /* frames freed by driver */\n bq->count = 0\n <-- Task A resumes -->\n ndo_xdp_xmit(bq->q[])\n /* use-after-free: frames already freed! */\n\nFix this by adding a local_lock_t to xdp_dev_bulk_queue and acquiring\nit in bq_enqueue() and __dev_flush(). These paths already run under\nlocal_bh_disable(), so use local_lock_nested_bh() which on non-RT is\na pure annotation with no overhead, and on PREEMPT_RT provides a\nper-CPU sleeping lock that serializes access to the bq." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploiting this vulnerability requires loading a BPF XDP program and creating a devmap, which is done via local syscalls (bpf() syscall and rtnetlink). This is not remotely reachable.\nAC:H - The vulnerability only manifests on PREEMPT_RT kernels, which is a non-default, EXPERT-only kernel configuration. This is a condition entirely beyond the attacker's control. Most deployed kernels do not use PREEMPT_RT.\nPR:L - Loading XDP programs and creating DEVMAPs requires CAP_NET_ADMIN, which can be obtained via user namespaces (unshare -Urn creates a network namespace where the user has CAP_NET_ADMIN). This makes it reachable by unprivileged local users.\nUI:N - No user interaction is required. The attacker can set up the XDP program, devmap, and trigger the race condition entirely on their own.\nS:U - The vulnerability affects the kernel within the same security authority. There is no cross-boundary escape (no VM escape, no IOMMU bypass).\nC:H - The use-after-free allows the attacker to control freed object contents via heap spraying, potentially enabling arbitrary kernel memory reads.\nI:H - The use-after-free on bq->q[] combined with count/array corruption provides write primitives that could be leveraged for control flow hijacking and arbitrary code execution in kernel context.\nA:H - The use-after-free and list corruption will reliably cause kernel crashes (oops/panic) when stale pointers in bq->q[] are dereferenced after being freed." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/devmap.c" ], "versions": [ { "version": "3253cb49cbad4772389d6ef55be75db1f97da910", "lessThan": "6c10b019785dc282c5f45d21e4a3f468b8fd6476", "status": "affected", "versionType": "git" }, { "version": "3253cb49cbad4772389d6ef55be75db1f97da910", "lessThan": "ab1a56c9d99189aa5c6e03940d06e40ba6a28240", "status": "affected", "versionType": "git" }, { "version": "3253cb49cbad4772389d6ef55be75db1f97da910", "lessThan": "1872e75375c40add4a35990de3be77b5741c252c", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/devmap.c" ], "versions": [ { "version": "6.18", "status": "affected" }, { "version": "0", "lessThan": "6.18", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.17", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.7", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "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": "6.18", "versionEndExcluding": "6.18.17" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "6.19.7" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "7.0" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/6c10b019785dc282c5f45d21e4a3f468b8fd6476" }, { "url": "https://git.kernel.org/stable/c/ab1a56c9d99189aa5c6e03940d06e40ba6a28240" }, { "url": "https://git.kernel.org/stable/c/1872e75375c40add4a35990de3be77b5741c252c" } ], "title": "bpf: Fix race in devmap on PREEMPT_RT", "x_generator": { "engine": "bippy-1.2.0" } } } }