Linux: Use After Free
CVE-2023-53636 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 5b4052aa956e11bcd19e50ca559eb38dcb46201b, d7d6dacf39ed102d7667721ca1700022c9c8b11a, 934406b2d42eaf3fc57f5546cc68ff7ab9680bb3 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.21% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 5b4052aa956e11bcd19e50ca559eb38dcb46201b or d7d6dacf39ed102d7667721ca1700022c9c8b11a or 934406b2d42eaf3fc57f5546cc68ff7ab9680bb3 or 7455b7007b9e93bcc2bc9c1c6c73a228e3152069, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.28 or 6.2.15 or 6.3.2, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | b56bae2dd6fda6baf3bb74af3812676eebdd52f2 up to, but not including, 5b4052aa956e11bcd19e50ca559eb38dcb46201b; b56bae2dd6fda6baf3bb74af3812676eebdd52f2 up to, but not including, d7d6dacf39ed102d7667721ca1700022c9c8b11a; b56bae2dd6fda6baf3bb74af3812676eebdd52f2 up to, but not including, 934406b2d42eaf3fc57f5546cc68ff7ab9680bb3; b56bae2dd6fda6baf3bb74af3812676eebdd52f2 up to, but not including, 7455b7007b9e93bcc2bc9c1c6c73a228e3152069; 6.1 | 5b4052aa956e11bcd19e50ca559eb38dcb46201b, d7d6dacf39ed102d7667721ca1700022c9c8b11a, 934406b2d42eaf3fc57f5546cc68ff7ab9680bb3, 7455b7007b9e93bcc2bc9c1c6c73a228e3152069 |
| Linux | Linux Kernel | 6.1 up to, but not including, 6.1.28; 6.2 up to, but not including, 6.2.15; 6.3 up to, but not including, 6.3.2 | 6.1.28, 6.2.15, 6.3.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
Official description
In the Linux kernel, the following vulnerability has been resolved: clk: microchip: fix potential UAF in auxdev release callback Similar to commit 1c11289b34ab ("peci: cpu: Fix use-after-free in adev_release()"), the auxiliary device is not torn down in the correct order. If auxiliary_device_add() fails, the release callback will be called twice, resulting in a UAF. Due to timing, the auxdev code in this driver "took inspiration" from the aforementioned commit, and thus its bugs too! Moving auxiliary_device_uninit() to the unregister callback instead avoids the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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