{"id":"CVE-2026-98509","kind":"vulnerability","aliases":["CVE-2026-98509"],"related":[],"title":"Linux kernel: virtio-gpu leaks a fence event on failed execbuffer calls","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/virtio: fix memory leak of fence event on execbuffer failure\n\nvirtio_gpu_execbuffer_ioctl() reserves a DRM event with\ndrm_event_reserve_init() when VIRTGPU_EXECBUF_RING_IDX selects a ring that\nuserspace has enabled polling for. virtio_gpu_init_submit() does this\nbefore the BO handles, the command buffer, the syncobj arrays and the\nin-fence are processed, so every later error path runs with the event\nalready pending, including plain argument validation failures such as an\ninvalid bo_handle or an in-syncobj that carries no fence.\n\nOn those paths, virtio_gpu_cleanup_submit() drops the out-fence without\ncancelling the event. The fence is freed without ever having been emitted,\ntaking the only driver-side pointer to the event with it. Closing the DRM\nfile does not help. drm_events_release() unlinks pending events but\ndeliberately leaves the freeing to the driver's later drm_send_event(),\nwhich never runs for an orphaned event, so the allocation is leaked\npermanently.\n\nFound when fuzzing the virtio driver with Syzkaller:\n\n\tBUG: memory leak\n\tunreferenced object 0xffff88802c176e80 (size 96):\n\tcomm \"syz.1.367\", pid 10561, jiffies 4294960122\n\thex dump (first 32 bytes):\n\t\t00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n\t\tc8 6e 17 2c 80 88 ff ff 00 00 00 00 00 00 00 00  .n.,............\n\tbacktrace (crc e1973c6b):\n\t\tkmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]\n\t\tslab_post_alloc_hook mm/slub.c:4597 [inline]\n\t\tslab_alloc_node mm/slub.c:4917 [inline]\n\t\t__kmalloc_cache_noprof+0x49d/0x6f0 mm/slub.c:5485\n\t\t_kmalloc_noprof include/linux/slab.h:988 [inline]\n\t\t_kzalloc_noprof include/linux/slab.h:1309 [inline]\n\t\tvirtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_submit.c:282 [inline]\n\t\tvirtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:398 [inline]\n\t\tvirtio_gpu_execbuffer_ioctl+0xbbf/0x1aa0 drivers/gpu/drm/virtio/virtgpu_submit.c:505\n\t\tdrm_ioctl_kernel+0x1f4/0x3e0 drivers/gpu/drm/drm_ioctl.c:817\n\t\tdrm_ioctl+0x5f4/0xc70 drivers/gpu/drm/drm_ioctl.c:914\n\t\tvfs_ioctl fs/ioctl.c:51 [inline]\n\t\t__do_sys_ioctl fs/ioctl.c:597 [inline]\n\t\t__se_sys_ioctl fs/ioctl.c:583 [inline]\n\t\t__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583\n\t\tdo_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n\t\tdo_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94\n\t\tentry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nFix by cancelling and freeing the DRM event on the execbuffer error path\nbefore dropping the fence. Clear the fence's event pointer after\ncancellation so it does not retain a dangling pointer.","summary":"When a virtio-gpu execbuffer ioctl fails argument validation after a poll event was reserved, the kernel never frees that event, so memory leaks permanently. The sources describe a memory leak found by fuzzing, not an attacker gaining code execution or data.","severity":"low","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["linux-kernel","runtime","virtio-gpu","virtual-machines"],"not_affected_if":["no-virtio-gpu-driver"],"how_to_check":"- `uname -r` and compare against the fixed kernel builds in the upstream stable commit for drm/virtio\n- `lsmod | grep virtio_gpu` to see whether the virtio-gpu driver is loaded at all","fix":"- Update the Linux kernel to a stable release that includes the drm/virtio fence event fix (exact version unknown from the sources)\n- Hosts without virtio-gpu loaded are not affected by this driver path","status":"open","published_at":"2026-10-18T16:17:02+00:00","first_seen_at":"2026-10-23T21:57:15+00:00","triaged_at":"2026-10-25T05:25:26+00:00","updated_at":"2026-10-25T05:25:26+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T05:25:26Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a stable release that includes the drm/virtio fence event fix (exact version unknown from the sources)\n- Hosts without virtio-gpu loaded are not affected by this driver path","reach":"local","title":"Linux kernel: virtio-gpu leaks a fence event on failed execbuffer calls","impact":"low","summary":"When a virtio-gpu execbuffer ioctl fails argument validation after a poll event was reserved, the kernel never frees that event, so memory leaks permanently. The sources describe a memory leak found by fuzzing, not an attacker gaining code execution or data.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","virtio-gpu","virtual-machines"],"confidence":0.6,"needs_auth":"unknown","worst_case":"unbounded kernel memory leak by local processes","analyst_note":"Confirm the fixed kernel version and stable commit ids from the kernel.org or NVD entry for CVE-2026-98509; sources give no CVSS score.","how_to_check":"- `uname -r` and compare against the fixed kernel builds in the upstream stable commit for drm/virtio\n- `lsmod | grep virtio_gpu` to see whether the virtio-gpu driver is loaded at all","needs_analyst":true,"not_affected_if":["no-virtio-gpu-driver"],"who_is_affected":"Systems running a Linux kernel with the virtio-gpu DRM driver loaded, typically virtual machines with virtio GPU devices. Exposure depends on userspace being able to issue DRM execbuffer ioctls, which usually means local processes with access to the DRM device node. Hosts without virtio-gpu can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.000765,"input_tokens":4497,"output_tokens":631,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'+0':335C,368C,375C,381C,405C,418C,427C '-2026':15A,18A '-98509':16A,19A '00':277C,278C,279C,280C,281C,282C,283C,284C,285C,286C,287C,288C,289C,290C,291C,292C,301C,302C,303C,304C,305C,306C,307C,308C '0xffff88802c176e80':263C '10561':269C '1309':347C '17':295C '282':355C '2c':296C '32':275C '398':362C '4294960122':271C '44':317C '4597':324C '4917':330C '505':371C '51':388C '5485':338C '583':400C,408C '597':394C '63':413C '64':417C,424C '6e':294C '80':297C '817':378C '88':298C '914':384C '94':421C '96':265C '988':342C 'alloc':246C,314C,321C,327C 'alreadi':152C 'arch/x86/entry/syscall_64.c':412C,420C 'argument':38B,156C 'array':135C 'attack':67B 'backtrac':310C 'bo':128C,163C 'buffer':132C 'bug':258C 'byte':276C 'c8':293C 'cach':333C 'call':13A 'cancel':187C,431C,453C 'carri':171C 'cleanup':179C 'clear':446C 'close':211C 'code':69B 'comm':266C 'command':131C 'crc':311C 'creat':353C 'cve':14A,17A 'dangl':460C 'data':72B 'deliber':225C 'describ':58B 'driver':203C,231C,255C 'driver-sid':202C 'drivers/gpu/drm/drm_ioctl.c':377C,383C 'drivers/gpu/drm/virtio/virtgpu_submit.c':354C,361C,370C 'drm':99C,102C,213C,218C,234C,372C,379C,435C 'drm/virtio':83C 'drop':181C,443C 'dump':273C 'e1973c6b':312C 'emit':198C 'enabl':117C 'entri':422C 'error':146C,440C 'event':9A,43B,51B,89C,100C,103C,151C,189C,208C,219C,223C,236C,243C,352C,436C,450C 'ever':195C 'everi':144C 'execbuf':108C 'execbuff':12A,35B,91C,95C,366C,439C 'execut':70B 'fail':11A,37B 'failur':92C,158C 'fenc':8A,88C,140C,173C,185C,191C,351C,445C,448C 'ff':299C,300C 'file':214C 'first':274C 'fix':84C,429C 'follow':78C 'found':62B,250C 'free':49B,228C,433C 'freed':193C 'fs/ioctl.c':387C,393C,399C,407C 'fuzz':64B,252C 'gain':68B 'gpu':5A,26B,34B,94C,121C,178C,350C,358C,365C 'handl':129C,164C 'help':217C 'hex':272C 'hook':322C 'hwframe':426C 'idx':110C 'in-fenc':138C 'in-syncobj':167C 'includ':154C 'include/linux/kmemleak.h':316C 'include/linux/slab.h':341C,346C 'init':105C,122C,359C 'inlin':318C,325C,331C,343C,348C,356C,363C,389C,395C,401C,414C 'invalid':162C 'ioctl':36B,96C,367C,373C,380C,386C,392C,398C,404C 'jiffi':270C 'kernel':2A,22B,47B,76C,374C 'kmalloc':332C,339C 'kmemleak':313C 'kzalloc':344C 'later':145C,233C 'leak':6A,54B,61B,86C,248C,260C 'leav':226C 'linux':1A,21B,75C 'linux-kernel':20B 'machin':29B 'memori':53B,60B,85C,259C 'mm/slub.c':323C,329C,337C 'n':309C 'never':48B,238C 'node':328C 'noprof':334C,340C,345C 'object':262C 'orphan':242C 'out-fenc':183C 'path':147C,176C,441C 'pend':153C,222C 'perman':55B,249C 'pid':268C 'plain':155C 'pointer':205C,451C,461C 'poll':42B,118C 'post':320C 'process':142C 'recurs':315C 'releas':220C 'reserv':45B,97C,104C 'resolv':82C 'retain':458C 'ring':109C,113C 'run':148C,239C 'runtim':23B 'se':396C 'select':111C 'send':235C 'side':204C 'size':264C 'slab':319C,326C 'sourc':57B 'submit':123C,180C,360C 'syncobj':134C,169C 'sys':391C,397C,403C 'syscal':410C,416C,423C 'syz.1.367':267C 'syzkal':257C 'take':199C 'unlink':221C 'unreferenc':261C 'userspac':115C 'valid':39B,157C 'vfs':385C 'virtgpu':107C 'virtio':4A,25B,33B,93C,120C,177C,254C,349C,357C,364C 'virtio-gpu':3A,24B,32B 'virtual':28B 'virtual-machin':27B 'vulner':79C 'without':186C,194C 'x116/0x800':419C 'x18e/0x210':406C 'x1f4/0x3e0':376C 'x49d/0x6f0':336C 'x5f4/0xc70':382C 'x64':402C,411C 'x77/0x7f':428C 'xbbf/0x1aa0':369C","nicknames":[],"mitigations":[],"who_affected":"Systems running a Linux kernel with the virtio-gpu DRM driver loaded, typically virtual machines with virtio GPU devices. Exposure depends on userspace being able to issue DRM execbuffer ioctls, which usually means local processes with access to the DRM device node. Hosts without virtio-gpu can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:02+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98509","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98509","severity":null,"published_at":"2026-10-18T16:17:02+00:00","modified_at":"2026-10-19T10:19:04+00:00","first_seen_at":"2026-10-23T21:57:15+00:00","fetched_at":"2026-10-23T22:28:56+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}