{"id":"CVE-2025-40323","url":"https://www.cyber-defence.io/tools/cve/CVE-2025-40323","generatedAt":"2026-10-28T03:23:19.806Z","title":"In the Linux kernel, the following vulnerability has been resolved: fbcon: Set fb_display[i]->mode to NULL when the mode is released Recently, we discovered the following issue through syzkaller: BUG: KASAN: slab-use-after-free in…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfbcon: Set fb_display[i]->mode to NULL when the mode is released\n\nRecently, we discovered the following issue through syzkaller:\n\nBUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0\nRead of size 4 at addr ff11000001b3c69c by task syz.xxx\n...\nCall Trace:\n <TASK>\n dump_stack_lvl+0xab/0xe0\n print_address_description.constprop.0+0x2c/0x390\n print_report+0xb9/0x280\n kasan_report+0xb8/0xf0\n fb_mode_is_equal+0x285/0x2f0\n fbcon_mode_deleted+0x129/0x180\n fb_set_var+0xe7f/0x11d0\n do_fb_ioctl+0x6a0/0x750\n fb_ioctl+0xe0/0x140\n __x64_sys_ioctl+0x193/0x210\n do_syscall_64+0x5f/0x9c0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nBased on experimentation and analysis, during framebuffer unregistration,\nonly the memory of fb_info->modelist is freed, without setting the\ncorresponding fb_display[i]->mode to NULL for the freed modes. This leads\nto UAF issues during subsequent accesses. Here's an example of reproduction\nsteps:\n1. With /dev/fb0 already registered in the system, load a kernel module\n   to register a new device /dev/fb1;\n2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP);\n3. Switch console from fb to VGA (to allow normal rmmod of the ko);\n4. Unload the kernel module, at this point fb1's modelist is freed, leaving\n   a wild pointer in fb_display[];\n5. Trigger the bug via system calls through fb0 attempting to delete a mode\n   from fb0.\n\nAdd a check in do_unregister_framebuffer(): if the mode to be freed exists\nin fb_display[], set the corresponding mode pointer to NULL.","published":"2025-12-08T01:16:05.000Z","lastModified":"2026-10-15T22:19:08.000Z","status":"Deferred","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"cwe":[],"affected":[],"epss":{"score":0.0014,"percentile":0.03343,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.14%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/39c2c1a2773aaf73e56906e5ef670114eb2d354f","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/468f78276a37f4c6499385a4ce28f4f57be6655d","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a1f3058930745d2b938b6b4f5bd9630dc74b26b7","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c079d42f70109512eee49123a843be91d8fa133f","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/de89d19f4f30d9a8de87b9d08c1bd35cb70576d8","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-40323","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}