{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2023-53747","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-12-08T01:18:04.279Z","datePublished":"2025-12-08T01:19:06.255Z","dateUpdated":"2026-08-05T09:15:45.787Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T09:15:45.787Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF\n\nAfter a call to console_unlock() in vcs_write() the vc_data struct can be\nfreed by vc_port_destruct(). Because of that, the struct vc_data pointer\nmust be reloaded in the while loop in vcs_write() after console_lock() to\navoid a UAF when vcs_size() is called.\n\nSyzkaller reported a UAF in vcs_size().\n\nBUG: KASAN: slab-use-after-free in vcs_size (drivers/tty/vt/vc_screen.c:215)\nRead of size 4 at addr ffff8880beab89a8 by task repro_vcs_size/4119\n\nCall Trace:\n <TASK>\n__asan_report_load4_noabort (mm/kasan/report_generic.c:380)\nvcs_size (drivers/tty/vt/vc_screen.c:215)\nvcs_write (drivers/tty/vt/vc_screen.c:664)\nvfs_write (fs/read_write.c:582 fs/read_write.c:564)\n...\n <TASK>\n\nAllocated by task 1213:\nkmalloc_trace (mm/slab_common.c:1064)\nvc_allocate (./include/linux/slab.h:559 ./include/linux/slab.h:680\n    drivers/tty/vt/vt.c:1078 drivers/tty/vt/vt.c:1058)\ncon_install (drivers/tty/vt/vt.c:3334)\ntty_init_dev (drivers/tty/tty_io.c:1303 drivers/tty/tty_io.c:1415\n    drivers/tty/tty_io.c:1392)\ntty_open (drivers/tty/tty_io.c:2082 drivers/tty/tty_io.c:2128)\nchrdev_open (fs/char_dev.c:415)\ndo_dentry_open (fs/open.c:921)\nvfs_open (fs/open.c:1052)\n...\n\nFreed by task 4116:\nkfree (mm/slab_common.c:1016)\nvc_port_destruct (drivers/tty/vt/vt.c:1044)\ntty_port_destructor (drivers/tty/tty_port.c:296)\ntty_port_put (drivers/tty/tty_port.c:312)\nvt_disallocate_all (drivers/tty/vt/vt_ioctl.c:662 (discriminator 2))\nvt_ioctl (drivers/tty/vt/vt_ioctl.c:903)\ntty_ioctl (drivers/tty/tty_io.c:2778)\n...\n\nThe buggy address belongs to the object at ffff8880beab8800\n which belongs to the cache kmalloc-1k of size 1024\nThe buggy address is located 424 bytes inside of\n freed 1024-byte region [ffff8880beab8800, ffff8880beab8c00)\n\nThe buggy address belongs to the physical page:\npage:00000000afc77580 refcount:1 mapcount:0 mapping:0000000000000000\n    index:0x0 pfn:0xbeab8\nhead:00000000afc77580 order:3 entire_mapcount:0 nr_pages_mapped:0\n    pincount:0\nflags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)\npage_type: 0xffffffff()\nraw: 000fffffc0010200 ffff888100042dc0 ffffea000426de00 dead000000000002\nraw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000\npage dumped because: kasan: bad access detected\n\nMemory state around the buggy address:\n ffff8880beab8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ffff8880beab8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n>ffff8880beab8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n                                  ^\n ffff8880beab8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ffff8880beab8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n==================================================================\nDisabling lock debugging due to kernel taint"}],"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 - Exploitation requires local access to character device nodes — write(2) on /dev/vcsN or /dev/vcsaN and an ioctl on a VT tty for VT_DISALLOCATE. There is no network or remote-peer reachability.\nAC:L - The attacker controls both sides of the race: one thread drives the write loop (which unconditionally drops console_lock every PAGE_SIZE chunk) while another calls VT_DISALLOCATE, and the window can be stretched indefinitely by backing the user buffer with userfaultfd or FUSE so copy_from_user stalls on demand. This makes the free-and-respray step reliable rather than opportunistic.\nPR:L - VT_DISALLOCATE carries no perm or capable() check whatsoever in vt_ioctl, so the only gate is DAC on /dev/vcs* and a VT fd — held by any tty-group member, any console-logged-in user via logind ACLs, or non-root console services on embedded systems. No capability or root privilege in the initial namespace is needed.\nUI:N - The attacker performs every step — allocating the VT, opening /dev/vcs*, issuing the write and the deallocation ioctl — from its own threads. No victim action is involved.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The stale vc_data is read after free (vcs_size, screenpos, vc_sw), and since the attacker can reclaim the kmalloc-1k slot with controlled data and set vc->vc_origin arbitrarily, the write path's read-modify-write sequences (vcs_scr_readw on the computed pointer) yield an arbitrary kernel-memory read primitive.\nI:H - vcs_write_buf derives its destination pointer from the freed object's vc_origin/vc_visible_origin and then writes attacker-supplied 16-bit values there, giving a controlled arbitrary kernel write; the viewed path additionally makes an indirect call through vc->vc_sw->con_screen_pos read out of freed memory, a direct control-flow hijack primitive leading to privilege escalation.\nA:H - Even unweaponized the bug is a slab use-after-free that reads and writes through a dangling pointer, producing KASAN splats, oopses, and kernel panics as syzkaller demonstrated, and it can be retriggered at will."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/tty/vt/vc_screen.c"],"versions":[{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"934de9a9b659785fed3e820bc0c813a460c71fea","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"0deff678157333d775af190f84696336cdcccd6d","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"a4e3c4c65ae8510e01352c9a4347e05c035b2ce2","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"11dddfbb7a4e62489b01074d6c04d9d1b42e4047","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"e3d1adcad5b73c7ed0c7edb35ab68abcaa45cf67","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"3338d0b9acde770ee588eead5cac32c25e7048fc","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"1de42e7653d6714a7507ba6696151a1fa028c69f","status":"affected","versionType":"git"},{"version":"ac751efa6a0d70f2c9daef5c7e3a92270f5c2dff","lessThan":"8fb9ea65c9d1338b0d2bb0a9122dc942cdd32357","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/tty/vt/vc_screen.c"],"versions":[{"version":"2.6.38","status":"affected"},{"version":"0","lessThan":"2.6.38","status":"unaffected","versionType":"semver"},{"version":"4.14.327","lessThanOrEqual":"4.14.*","status":"unaffected","versionType":"semver"},{"version":"4.19.284","lessThanOrEqual":"4.19.*","status":"unaffected","versionType":"semver"},{"version":"5.4.244","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.181","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.113","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.30","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.3.4","lessThanOrEqual":"6.3.*","status":"unaffected","versionType":"semver"},{"version":"6.4","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":"2.6.38","versionEndExcluding":"4.14.327"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"4.19.284"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"5.4.244"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"5.10.181"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"5.15.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.1.30"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.3.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.38","versionEndExcluding":"6.4"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/934de9a9b659785fed3e820bc0c813a460c71fea"},{"url":"https://git.kernel.org/stable/c/0deff678157333d775af190f84696336cdcccd6d"},{"url":"https://git.kernel.org/stable/c/a4e3c4c65ae8510e01352c9a4347e05c035b2ce2"},{"url":"https://git.kernel.org/stable/c/11dddfbb7a4e62489b01074d6c04d9d1b42e4047"},{"url":"https://git.kernel.org/stable/c/e3d1adcad5b73c7ed0c7edb35ab68abcaa45cf67"},{"url":"https://git.kernel.org/stable/c/3338d0b9acde770ee588eead5cac32c25e7048fc"},{"url":"https://git.kernel.org/stable/c/1de42e7653d6714a7507ba6696151a1fa028c69f"},{"url":"https://git.kernel.org/stable/c/8fb9ea65c9d1338b0d2bb0a9122dc942cdd32357"}],"title":"vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF","x_generator":{"engine":"bippy-1.2.0"}}}}