Linux Kernel up to 5.17.1 cirrusfb_check_pixclock divide by zero

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 5.17.1. Impacted is the function cirrusfb_check_pixclock. Performing a manipulation results in divide by zero. This vulnerability is reported as CVE-2021-47641. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 5.17.1. It has been classified as critical. This affects the function cirrusfb_check_pixclock. The manipulation with an unknown input leads to a divide by zero vulnerability. CWE is classifying the issue as CWE-369. The product divides a value by zero. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: video: fbdev: cirrusfb: check pixclock to avoid divide by zero Do a sanity check on pixclock value to avoid divide by zero. If the pixclock value is zero, the cirrusfb driver will round up pixclock to get the derived frequency as close to maxclock as possible. Syzkaller reported a divide error in cirrusfb_check_pixclock. divide error: 0000 [#1] SMP KASAN PTI CPU: 0 PID: 14938 Comm: cirrusfb_test Not tainted 5.15.0-rc6 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2 RIP: 0010:cirrusfb_check_var+0x6f1/0x1260 Call Trace: fb_set_var+0x398/0xf90 do_fb_ioctl+0x4b8/0x6f0 fb_ioctl+0xeb/0x130 __x64_sys_ioctl+0x19d/0x220 do_syscall_64+0x3a/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2021-47641 since 02/26/2025. The exploitability is told to be difficult. Technical details are known, but no exploit is available.

Upgrading to version 4.9.311, 4.14.276, 4.19.238, 5.4.189, 5.10.110, 5.15.33, 5.16.19 or 5.17.2 eliminates this vulnerability. Applying the patch c656d04247a2654ede5cead2ecbf83431dad5261/1d3fb46439ad4e8f0c5739eb33d1875ac9e0f135/40b13e3d85744210db13457785646634e2d056bd/53a2088a396cfa1da92690a1da289634cd73bf0d/8c7e2141fb89c620ab4e41512e262fbf25b8260d/6fe23ff94e7840097202e85c148688940b37c9b1/45800c42ef000f417270bcfc08630e42486fca99/e498b504f8c81b07efab9febf8503448de4dc9cf/5c6f402bdcf9e7239c6bc7087eda71ac99b31379 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2021-34663). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 4.9.310
• 4.14.275
• 4.19.237
• 5.4.188
• 5.10.109
• 5.15.0
• 5.15.1
• 5.15.2
• 5.15.3
• 5.15.4
• 5.15.5
• 5.15.6
• 5.15.7
• 5.15.8
• 5.15.9
• 5.15.10
• 5.15.11
• 5.15.12
• 5.15.13
• 5.15.14
• 5.15.15
• 5.15.16
• 5.15.17
• 5.15.18
• 5.15.19
• 5.15.20
• 5.15.21
• 5.15.22
• 5.15.23
• 5.15.24
• 5.15.25
• 5.15.26
• 5.15.27
• 5.15.28
• 5.15.29
• 5.15.30
• 5.15.31
• 5.15.32
• 5.16.0
• 5.16.1
• 5.16.2
• 5.16.3
• 5.16.4
• 5.16.5
• 5.16.6
• 5.16.7
• 5.16.8
• 5.16.9
• 5.16.10
• 5.16.11
• 5.16.12
• 5.16.13
• 5.16.14
• 5.16.15
• 5.16.16
• 5.16.17
• 5.16.18
• 5.17.0
• 5.17.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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CVSSv2info

Exploitinginfo

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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