Kernel: Use After Free
CVE-2023-4208 is a high-severity use after free vulnerability in Kernel from 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 version 6.5 as the first without the flaw, so updating Kernel to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.31% 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 Kernel to 6.5 or a later version.
- Update Linux Kernel to 4.14.322 or 4.19.291 or 5.4.253 or 5.10.190, whichever matches your release line, or a later version.
- Read the advisory on git.kernel.org for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Kernel | 3.18 up to, but not including, 6.5 | 6.5 |
| Linux | Linux Kernel | 3.18 up to, but not including, 4.14.322; 4.15 up to, but not including, 4.19.291; 4.20 up to, but not including, 5.4.253; 5.5 up to, but not including, 5.10.190; 5.11 up to, but not including, 5.15.126; 5.16 up to, but not including, 6.1.45; 6.2 up to, but not including, 6.4.10 | 4.14.322, 4.19.291, 5.4.253, 5.10.190, 5.15.126, 6.1.45 |
| Debian | Debian Linux | 12.0 | Not stated |
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.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA (google.com) |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
A use-after-free vulnerability in the Linux kernel's net/sched: cls_u32 component can be exploited to achieve local privilege escalation. When u32_change() is called on an existing filter, the whole tcf_result struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcf_unbind_filter() is always called on the old instance in the success path, decreasing filter_cnt of the still referenced class and allowing it to be deleted, leading to a use-after-free. We recommend upgrading past commit 3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81.
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
Advisories
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2024/01/msg00004.htmlThird Party Advisory
- debian.org/security/2023/dsa-5492Third Party Advisory
Other vulnerabilities in Kernel
- 7.1 High severity
- 7.8 High severity
Linux Kernel Use-After-Free Exploited
- 7.8 High severity
- 7.1 High severity
- 7.4 High severity
- 7.0 High severity
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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