7.8High
Linux Linux Kernel
CVE-2021-33034
In the Linux kernel before 5.12.4, net/bluetooth/hci_event.c has a use-after-free when destroying an hci_chan, aka CID-5c4c8c954409. This leads to writing an arbitrary value.
What this means for your business
- It affects Linux Kernel. It matters if your company, or a supplier that handles your data, runs it.
- Code showing how to exploit it has been published, but real attacks have not been confirmed.
- An attacker can use it only with access to the machine itself, with an ordinary user login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 0.8% chance of attack attempts being seen in the next 30 days, ranking above 55% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Linux Kernel, and which version. The affected versions are listed further down this page.
- 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
Not sure if your company is exposed?
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Scoring
- CVSS
- 7.8 (v3.1)
- Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H- Weakness
- CWE-416
- Assigned by
- cve@mitre.org
Dates
- Published
- 2021-05-14
- Last modified
- 2026-08-13
- Sources
- NVD
Affected products
- Linux Linux Kernel- 4.4.269, 4.5 - 4.9.269, 4.10 - 4.14.233, 4.15 - 4.19.191, 4.20 - 5.4.119, 5.5 - 5.10.37, 5.11 - 5.11.21, 5.12 - 5.12.4
- Fedoraproject Fedora34
- Debian Debian Linux9.0
As listed in the NVD configuration data. Not a statement about your estate.
References
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12.4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5c4c8c9544099bb9043a10a5318130a943e32fc3
- https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html
- https://lists.debian.org/debian-lts-announce/2021/06/msg00020.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GI7Z7UBWBGD3ABNIL2DC7RQDCGA4UVQW/
- https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-hci_send_acl
- https://syzkaller.appspot.com/bug?id=2e1943a94647f7732dd6fc60368642d6e8dc91b1
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12.4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5c4c8c9544099bb9043a10a5318130a943e32fc3
- https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html
- https://lists.debian.org/debian-lts-announce/2021/06/msg00020.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GI7Z7UBWBGD3ABNIL2DC7RQDCGA4UVQW/
- https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-hci_send_acl
- https://syzkaller.appspot.com/bug?id=2e1943a94647f7732dd6fc60368642d6e8dc91b1