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CVE-2025-40323
published 2025-12-08

CVE-2025-40323: 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…

PriorityP340high7.8CVSS 3.1
AVLACLPRLUINSUCHIHAH
EPSS
0.12%
2.5th percentile
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 fb_mode_is_equal+0x285/0x2f0 Read of size 4 at addr ff11000001b3c69c by task syz.xxx ... Call Trace: dump_stack_lvl+0xab/0xe0 print_address_description.constprop.0+0x2c/0x390 print_report+0xb9/0x280 kasan_report+0xb8/0xf0 fb_mode_is_equal+0x285/0x2f0 fbcon_mode_deleted+0x129/0x180 fb_set_var+0xe7f/0x11d0 do_fb_ioctl+0x6a0/0x750 fb_ioctl+0xe0/0x140 __x64_sys_ioctl+0x193/0x210 do_syscall_64+0x5f/0x9c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Based on experimentation and analysis, during framebuffer unregistration, only the memory of fb_info->modelist is freed, without setting the corresponding fb_display[i]->mode to NULL for the freed modes. This leads to UAF issues during subsequent accesses. Here's an example of reproduction steps: 1. With /dev/fb0 already registered in the system, load a kernel module to register a new device /dev/fb1; 2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP); 3. Switch console from fb to VGA (to allow normal rmmod of the ko); 4. Unload the kernel module, at this point fb1's modelist is freed, leaving a wild pointer in fb_display[]; 5. Trigger the bug via system calls through fb0 attempting to delete a mode from fb0. Add a check in do_unregister_framebuffer(): if the mode to be freed exists in fb_display[], set the corresponding mode pointer to NULL.

Affected

46 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
debianlinux-6.1< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
linuxlinux
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 39c2c1a2773aaf73e56906e5ef670114eb2d354f39c2c1a2773aaf73e56906e5ef670114eb2d354f
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 468f78276a37f4c6499385a4ce28f4f57be6655d468f78276a37f4c6499385a4ce28f4f57be6655d
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c079d42f70109512eee49123a843be91d8fa133fc079d42f70109512eee49123a843be91d8fa133f
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < de89d19f4f30d9a8de87b9d08c1bd35cb70576d8de89d19f4f30d9a8de87b9d08c1bd35cb70576d8
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < a1f3058930745d2b938b6b4f5bd9630dc74b26b7a1f3058930745d2b938b6b4f5bd9630dc74b26b7
linuxlinux_kernel>= 0 < 6.1.159-16.1.159-1
linuxlinux_kernel>= 0 < 6.12.63-16.12.63-1
linuxlinux_kernel>= 0 < 6.17.8-16.17.8-1
linuxlinux_kernel>= 0 < 6.8.0-106.1066.8.0-106.106
linuxlinux_kernel>= 0 < 6.17.0-14.146.17.0-14.14
linuxlinux_kernel>= 2.6.12 < 6.1.1596.1.159
linuxlinux_kernel>= 6.13.0 < 6.17.86.17.8
linuxlinux_kernel>= 6.2.0 < 6.6.1176.6.117
linuxlinux_kernel>= 6.7.0 < 6.12.586.12.58
msrcazl3_kernel_6.6.112.1-2_on_azure_linux_3.0
ubuntulinux
ubuntulinux-aws
ubuntulinux-aws-5.15
ubuntulinux-aws-fips
ubuntulinux-azure-5.15
ubuntulinux-azure-fde

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
osv3.2LOW
vendor_ubuntu7.8HIGH
vendor_redhat5.8MEDIUM
vendor_msrc5.5MEDIUM
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