Linux: Use After Free
CVE-2022-48801 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 b7f54894aa7517d2b6c797a499b9f491e9db9083, 202071d2518537866d291aa7cf26af54e674f4d4, c72ea20503610a4a7ba26c769357d31602769c01 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 b7f54894aa7517d2b6c797a499b9f491e9db9083 or 202071d2518537866d291aa7cf26af54e674f4d4 or c72ea20503610a4a7ba26c769357d31602769c01, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.24 or 5.16.10, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | f73f7f4da581875f9b1f2fb8ebd1ab15ed634488 up to, but not including, b7f54894aa7517d2b6c797a499b9f491e9db9083; f73f7f4da581875f9b1f2fb8ebd1ab15ed634488 up to, but not including, 202071d2518537866d291aa7cf26af54e674f4d4; f73f7f4da581875f9b1f2fb8ebd1ab15ed634488 up to, but not including, c72ea20503610a4a7ba26c769357d31602769c01; 5.13 | b7f54894aa7517d2b6c797a499b9f491e9db9083, 202071d2518537866d291aa7cf26af54e674f4d4, c72ea20503610a4a7ba26c769357d31602769c01 |
| Linux | Linux Kernel | 5.13 up to, but not including, 5.15.24; 5.16 up to, but not including, 5.16.10; 5.17 | 5.15.24, 5.16.10 |
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 |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: iio: buffer: Fix file related error handling in IIO_BUFFER_GET_FD_IOCTL If we fail to copy the just created file descriptor to userland, we try to clean up by putting back 'fd' and freeing 'ib'. The code uses put_unused_fd() for the former which is wrong, as the file descriptor was already published by fd_install() which gets called internally by anon_inode_getfd(). This makes the error handling code leaving a half cleaned up file descriptor table around and a partially destructed 'file' object, allowing userland to play use-after-free tricks on us, by abusing the still usable fd and making the code operate on a dangling 'file->private_data' pointer. Instead of leaving the kernel in a partially corrupted state, don't attempt to explicitly clean up and leave this to the process exit path that'll release any still valid fds, including the one created by the previous call to anon_inode_getfd(). Simply return -EFAULT to indicate the error.
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
Recent Use After Free vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Spotted an error? Tell us.