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Review reviewHigh

CVE-2021-47281

Linux Linux, linux kernel

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Fix race of snd_seq_timer_open() The timer instance per queue is exclusive, and snd_seq_timer_open() should have managed the concurrent accesses. It looks as if it's checking the already existing timer instance at the beginning, but it's not right, because there is no protection, hence any later concurrent call of snd_seq_timer_open() may override the timer instance easily. This may result in UAF, as the leftover timer instance can keep running while the queue itself gets closed, as spotted by syzkaller recently....

CVSS
7
EPSS
0.24%
14.7% percentile
CISA KEV
Not listed
Published
2024.05.22
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.24%
Technical severityCVSS 7

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Fix race of snd_seq_timer_open() The timer instance per queue is exclusive, and snd_seq_timer_open() should have managed the concurrent accesses. It looks as if it's checking the already existing timer instance at the beginning, but it's not right, because there is no protection, hence any later concurrent call of snd_seq_timer_open() may override the timer instance easily. This may result in UAF, as the leftover timer instance can keep running while the queue itself gets closed, as spotted by syzkaller recently....

Affected product and versions

Product
Linux Linux, linux kernel
Affected versions
>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < bd7d88b0874f82f7b29d1a53e574cedaf23166ba, >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 536a7646c00a0f14fee49e5e313109e5da2f6031, >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 83e197a8414c0ba545e7e3916ce05f836f349273, >= 2.6.12, < 5.10.44, >= 5.11 < 5.12.11, 5.13
Fixed versions
5.10.44, 5.12.11

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux kernel and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-416
CVE-2021-47281 — Linux Linux, linux kernel | SECUFOCUS NOW