Linux: Use After Free
CVE-2024-40935 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 320ba9cbca78be79c912143bbba1d1b35ca55cf0, 3bf0b8030296e9ee60d3d4c15849ad9ac0b47081, e73fac95084839c5178d97e81c6a2051251bdc00 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 0.26% 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 320ba9cbca78be79c912143bbba1d1b35ca55cf0 or 3bf0b8030296e9ee60d3d4c15849ad9ac0b47081 or e73fac95084839c5178d97e81c6a2051251bdc00 or 85e833cd7243bda7285492b0653c3abb1e2e757b, 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, 320ba9cbca78be79c912143bbba1d1b35ca55cf0; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, 3bf0b8030296e9ee60d3d4c15849ad9ac0b47081; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, e73fac95084839c5178d97e81c6a2051251bdc00; c8383054506c77b814489c09877b5db83fd4abf2 up to, but not including, 85e833cd7243bda7285492b0653c3abb1e2e757b; 5.19 | 320ba9cbca78be79c912143bbba1d1b35ca55cf0, 3bf0b8030296e9ee60d3d4c15849ad9ac0b47081, e73fac95084839c5178d97e81c6a2051251bdc00, 85e833cd7243bda7285492b0653c3abb1e2e757b |
| 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: flush all requests after setting CACHEFILES_DEAD In ondemand mode, when the daemon is processing an open request, if the kernel flags the cache as CACHEFILES_DEAD, the cachefiles_daemon_write() will always return -EIO, so the daemon can't pass the copen to the kernel. Then the kernel process that is waiting for the copen triggers a hung_task. Since the DEAD state is irreversible, it can only be exited by closing /dev/cachefiles. Therefore, after calling cachefiles_io_error() to mark the cache as CACHEFILES_DEAD, if in ondemand mode, flush all requests to avoid the above hungtask. We may still be able to read some of the cached data before closing the fd of /dev/cachefiles. Note that this relies on the patch that adds reference counting to the req, otherwise it may UAF.
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
- 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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