{"id":"CVE-2021-47338","state":"PUBLISHED","title":"fbmem: Do not delete the mode that is still in use","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfbmem: Do not delete the mode that is still in use\n\nThe execution of fb_delete_videomode() is not based on the result of the\nprevious fbcon_mode_deleted(). As a result, the mode is directly deleted,\nregardless of whether it is still in use, which may cause UAF.\n\n==================================================================\nBUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \\\ndrivers/video/fbdev/core/modedb.c:924\nRead of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962\n\nCPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...\nCall Trace:\n __dump_stack lib/dump_stack.c:77 [inline]\n dump_stack+0x137/0x1be lib/dump_stack.c:118\n print_address_description+0x6c/0x640 mm/kasan/report.c:385\n __kasan_report mm/kasan/report.c:545 [inline]\n kasan_report+0x13d/0x1e0 mm/kasan/report.c:562\n fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924\n fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746\n fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975\n do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108\n vfs_ioctl fs/ioctl.c:48 [inline]\n __do_sys_ioctl fs/ioctl.c:753 [inline]\n __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739\n do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n\nFreed by task 18960:\n kasan_save_stack mm/kasan/common.c:48 [inline]\n kasan_set_track+0x3d/0x70 mm/kasan/common.c:56\n kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355\n __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422\n slab_free_hook mm/slub.c:1541 [inline]\n slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574\n slab_free mm/slub.c:3139 [inline]\n kfree+0xca/0x3d0 mm/slub.c:4121\n fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104\n fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978\n do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108\n vfs_ioctl fs/ioctl.c:48 [inline]\n __do_sys_ioctl fs/ioctl.c:753 [inline]\n __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739\n do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46\n entry_SYSCALL_64_after_hwframe+0x44/0xa9","publishedAt":"2024-05-21T14:35:47.028Z","updatedAt":"2026-08-05T08:47:17.872Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"359311b85ebec7c07c3a08ae2f3def946cad33fa","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"087bff9acd2ec6db3f61aceb3224bde90fe0f7f8","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"f193509afc7ff37a46862610c93b896044d5b693","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"d6e76469157d8f240e5dec6f8411aa8d306b1126","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"0af778269a522c988ef0b4188556aba97fb420cc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbmem.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.134","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.52","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.19","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13.4","status":"unaffected","lessThanOrEqual":"5.13.*","versionType":"semver"},{"version":"5.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbmem.c"]}],"references":["https://git.kernel.org/stable/c/359311b85ebec7c07c3a08ae2f3def946cad33fa","https://git.kernel.org/stable/c/087bff9acd2ec6db3f61aceb3224bde90fe0f7f8","https://git.kernel.org/stable/c/f193509afc7ff37a46862610c93b896044d5b693","https://git.kernel.org/stable/c/d6e76469157d8f240e5dec6f8411aa8d306b1126","https://git.kernel.org/stable/c/0af778269a522c988ef0b4188556aba97fb420cc"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47338.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47338","state":"PUBLISHED","datePublished":"2024-05-21T14:35:47.028Z","dateUpdated":"2026-08-05T08:47:17.872Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-05-21T14:28:16.978Z"},"containers":{"cna":{"title":"fbmem: Do not delete the mode that is still in use","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfbmem: Do not delete the mode that is still in use\n\nThe execution of fb_delete_videomode() is not based on the result of the\nprevious fbcon_mode_deleted(). As a result, the mode is directly deleted,\nregardless of whether it is still in use, which may cause UAF.\n\n==================================================================\nBUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \\\ndrivers/video/fbdev/core/modedb.c:924\nRead of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962\n\nCPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ...\nCall Trace:\n __dump_stack lib/dump_stack.c:77 [inline]\n dump_stack+0x137/0x1be lib/dump_stack.c:118\n print_address_description+0x6c/0x640 mm/kasan/report.c:385\n __kasan_report mm/kasan/report.c:545 [inline]\n kasan_report+0x13d/0x1e0 mm/kasan/report.c:562\n fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924\n fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746\n fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975\n do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108\n vfs_ioctl fs/ioctl.c:48 [inline]\n __do_sys_ioctl fs/ioctl.c:753 [inline]\n __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739\n do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n\nFreed by task 18960:\n kasan_save_stack mm/kasan/common.c:48 [inline]\n kasan_set_track+0x3d/0x70 mm/kasan/common.c:56\n kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355\n __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422\n slab_free_hook mm/slub.c:1541 [inline]\n slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574\n slab_free mm/slub.c:3139 [inline]\n kfree+0xca/0x3d0 mm/slub.c:4121\n fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104\n fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978\n do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108\n vfs_ioctl fs/ioctl.c:48 [inline]\n __do_sys_ioctl fs/ioctl.c:753 [inline]\n __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739\n do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46\n entry_SYSCALL_64_after_hwframe+0x44/0xa9"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"359311b85ebec7c07c3a08ae2f3def946cad33fa","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"087bff9acd2ec6db3f61aceb3224bde90fe0f7f8","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"f193509afc7ff37a46862610c93b896044d5b693","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"d6e76469157d8f240e5dec6f8411aa8d306b1126","versionType":"git"},{"version":"13ff178ccd6d3b8074c542a911300b79c4eec255","status":"affected","lessThan":"0af778269a522c988ef0b4188556aba97fb420cc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbmem.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.134","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.52","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.19","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13.4","status":"unaffected","lessThanOrEqual":"5.13.*","versionType":"semver"},{"version":"5.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbmem.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/359311b85ebec7c07c3a08ae2f3def946cad33fa"},{"url":"https://git.kernel.org/stable/c/087bff9acd2ec6db3f61aceb3224bde90fe0f7f8"},{"url":"https://git.kernel.org/stable/c/f193509afc7ff37a46862610c93b896044d5b693"},{"url":"https://git.kernel.org/stable/c/d6e76469157d8f240e5dec6f8411aa8d306b1126"},{"url":"https://git.kernel.org/stable/c/0af778269a522c988ef0b4188556aba97fb420cc"}],"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 - Triggered via local ioctl(FBIOPUT_VSCREENINFO) on /dev/fbN through do_fb_ioctl → fb_set_var; there is no network or adjacent-protocol path into fbmem/fbcon.\nAC:L - The attacker fully controls mode setup and FB_ACTIVATE_INV_MODE deletion; ignoring fbcon_mode_deleted()'s in-use result deterministically frees a modelist entry while fb_display[].mode still points at it, with no attacker-independent race or layout requirement.\nPR:L - do_fb_ioctl/FBIOPUT_VSCREENINFO performs no capability check; access is only DAC on /dev/fbN, which seated users, video-group members, and embedded/Android graphics processes commonly have without init-namespace root.\nUI:N - The attacker opens the framebuffer device and issues the ioctl sequence directly; no separate victim action is required.\nS:U - Impact is kernel heap use-after-free and potential privilege escalation within the same host security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is a use-after-free of a groomable kmalloc fb_modelist object whose dangling mode pointer is later read (e.g. fb_mode_is_equal/display_to_var), enabling heap disclosure per UAF scoring guidance.\nI:H - UAF of a sprayable slab object allows reclaim/type confusion and corruption of kernel state through subsequent fbcon/fb_set_var paths, enabling write primitives and control-flow hijack.\nA:H - The syzkaller/KASAN report is a slab use-after-free that oopses in fb_mode_is_equal(); dereferencing the dangling pointer after reclaim or page return can panic the kernel."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:47:17.872Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.4.134"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.10.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.12.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.13.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.14"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2024-06-12T15:00:51.209603Z","id":"CVE-2021-47338","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-06-12T15:01:02.502Z"}},{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/359311b85ebec7c07c3a08ae2f3def946cad33fa","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/087bff9acd2ec6db3f61aceb3224bde90fe0f7f8","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/f193509afc7ff37a46862610c93b896044d5b693","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/d6e76469157d8f240e5dec6f8411aa8d306b1126","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/0af778269a522c988ef0b4188556aba97fb420cc","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:32:08.605Z"}}]}}}