Linux: Use After Free
CVE-2024-40913 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 eac51d9daacd61dcc93333ff6a890cf3efc8c1c0, d2d3eb377a5d081bf2bed177d354a4f59b74da88, b9f58cdae6a364a3270fd6b6a46e0fd4f7f8ce32 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 0.29% 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 eac51d9daacd61dcc93333ff6a890cf3efc8c1c0 or d2d3eb377a5d081bf2bed177d354a4f59b74da88 or b9f58cdae6a364a3270fd6b6a46e0fd4f7f8ce32 or 4b4391e77a6bf24cba2ef1590e113d9b73b11039, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.95 or 6.6.35 or 6.9.6, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, eac51d9daacd61dcc93333ff6a890cf3efc8c1c0; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, d2d3eb377a5d081bf2bed177d354a4f59b74da88; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, b9f58cdae6a364a3270fd6b6a46e0fd4f7f8ce32; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, 4b4391e77a6bf24cba2ef1590e113d9b73b11039; 5.19 | eac51d9daacd61dcc93333ff6a890cf3efc8c1c0, d2d3eb377a5d081bf2bed177d354a4f59b74da88, b9f58cdae6a364a3270fd6b6a46e0fd4f7f8ce32, 4b4391e77a6bf24cba2ef1590e113d9b73b11039 |
| Linux | Linux Kernel | 5.19 up to, but not including, 6.1.95; 6.2 up to, but not including, 6.6.35; 6.7 up to, but not including, 6.9.6; 6.10 | 6.1.95, 6.6.35, 6.9.6 |
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: cachefiles: defer exposing anon_fd until after copy_to_user() succeeds After installing the anonymous fd, we can now see it in userland and close it. However, at this point we may not have gotten the reference count of the cache, but we will put it during colse fd, so this may cause a cache UAF. So grab the cache reference count before fd_install(). In addition, by kernel convention, fd is taken over by the user land after fd_install(), and the kernel should not call close_fd() after that, i.e., it should call fd_install() after everything is ready, thus fd_install() is called after copy_to_user() succeeds.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Use After Free vulnerabilities
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- 7.8 High severity
- 7.8 High severity
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