CVE-2021-47182

CVE-2021-47182 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: core: Fix scsi_mode_sense() buffer length handling Several problems exist with scsi_mode_sense() buffer length handling: 1) The allocation length field of the MODE SENSE(10) command is 16-bits, occupying bytes 7 and 8 of the CDB. With this command, access to mode pages larger than 255 bytes is thus possible. However, the CDB allocation length field is set by assigning len to byte 8 only, thus truncating buffer length larger than 255. 2) If scsi_mode_sense() is called with len smaller than 8 with sdev->use_10_for_ms set, or smaller than 4 otherwise, the buffer length is increased to 8 and 4 respectively, and the buffer is zero filled with these increased values, thus corrupting the memory following the buffer. Fix these 2 problems by using put_unaligned_be16() to set the allocation length field of MODE SENSE(10) CDB and by returning an error when len is too small. Furthermore, if len is larger than 255B, always try MODE SENSE(10) first, even if the device driver did not set sdev->use_10_for_ms. In case of invalid opcode error for MODE SENSE(10), access to mode pages larger than 255 bytes are not retried using MODE SENSE(6). To avoid buffer length overflows for the MODE_SENSE(10) case, check that len is smaller than 65535 bytes. While at it, also fix the folowing: * Use get_unaligned_be16() to retrieve the mode data length and block descriptor length fields of the mode sense reply header instead of using an open coded calculation. * Fix the kdoc dbd argument explanation: the DBD bit stands for Disable Block Descriptor, which is the opposite of what the dbd argument description was.

Frequently asked questions

What is CVE-2021-47182?
In the Linux kernel, the following vulnerability has been resolved: scsi: core: Fix scsi_mode_sense() buffer length handling Several problems exist with scsi_mode_sense() buffer length handling: 1) The allocation length field of the MODE SENSE(10) command is 16-bits, occupying bytes 7 and 8 of the CDB. With this command, access to mode pages larger than 255 bytes is thus possible. However, the CDB allocation length field is set by assigning len to byte 8 only, thus truncating buffer length larger than 255. 2) If scsi_mode_sense() is called with len smaller than 8 with sdev->use_10_for_ms set, or smaller than 4 otherwise, the buffer length is increased to 8 and 4 respectively, and the buffer is zero filled with these increased values, thus corrupting the memory following the buffer. Fix these 2 problems by using put_unaligned_be16() to set the allocation length field of MODE SENSE(10) CDB and by returning an error when len is too small. Furthermore, if len is larger than 255B, always try MODE SENSE(10) first, even if the device driver did not set sdev->use_10_for_ms. In case of invalid opcode error for MODE SENSE(10), access to mode pages larger than 255 bytes are not retried using MODE SENSE(6). To avoid buffer length overflows for the MODE_SENSE(10) case, check that len is smaller than 65535 bytes. While at it, also fix the folowing: * Use get_unaligned_be16() to retrieve the mode data length and block descriptor length fields of the mode sense reply header instead of using an open coded calculation. * Fix the kdoc dbd argument explanation: the DBD bit stands for Disable Block Descriptor, which is the opposite of what the dbd argument description was.
How severe is CVE-2021-47182?
CVE-2021-47182 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-47182 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-47182?
CVE-2021-47182 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-47182?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2021-47182 have an EU (EUVD) identifier?
Yes. CVE-2021-47182 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-33830.
When was CVE-2021-47182 published?
CVE-2021-47182 was published on 2024-04-10 and last updated on 2026-06-17.

References

Affected products (1)

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