CVE-2021-47281
What it is
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. For avoiding the race, add a proper check at the assignment of tmr->timeri again, and return -EBUSY if it's been already registered.
At a glance
- Exploitability
- Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.
- Exploit odds
- 0.2% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.2% in the next 30 days (EPSS).
- Severity: 7.8 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.2% · EPSS, next 30 days
- Weakness
- CWE-416 · Use after free
- Record status
- Modified
Affected
- Linux Kernel < 5.10.44
- Linux Kernel < 5.12.11
- Linux Kernel 5.13
Attack profile CVSS 3.1 · 7.8
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2021-47281.md and follow it. Check whether this project is affected by CVE-2021-47281. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://git.kernel.org/stable/c/536a7646c00a0f14fee49e5e313109e5da2f6031
- https://git.kernel.org/stable/c/83e197a8414c0ba545e7e3916ce05f836f349273
- https://git.kernel.org/stable/c/bd7d88b0874f82f7b29d1a53e574cedaf23166ba
- https://git.kernel.org/stable/c/536a7646c00a0f14fee49e5e313109e5da2f6031
- https://git.kernel.org/stable/c/83e197a8414c0ba545e7e3916ce05f836f349273
- https://git.kernel.org/stable/c/bd7d88b0874f82f7b29d1a53e574cedaf23166ba
References
- https://git.kernel.org/stable/c/536a7646c00a0f14fee49e5e313109e5da2f6031
- https://git.kernel.org/stable/c/83e197a8414c0ba545e7e3916ce05f836f349273
- https://git.kernel.org/stable/c/bd7d88b0874f82f7b29d1a53e574cedaf23166ba
- https://git.kernel.org/stable/c/536a7646c00a0f14fee49e5e313109e5da2f6031
- https://git.kernel.org/stable/c/83e197a8414c0ba545e7e3916ce05f836f349273
- https://git.kernel.org/stable/c/bd7d88b0874f82f7b29d1a53e574cedaf23166ba