Linux: Use After Free
CVE-2022-49995 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 f96b9f7c1676923bce871e728bb49c0dfa5013cc, 9a6c710f3bc10bc9cc23e1c080b53245b7f9d5b7, f87904c075515f3e1d8f4a7115869d3b914674fd 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 0.27% 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 f96b9f7c1676923bce871e728bb49c0dfa5013cc or 9a6c710f3bc10bc9cc23e1c080b53245b7f9d5b7 or f87904c075515f3e1d8f4a7115869d3b914674fd, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.64 or 5.19.6, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 45a2966fd64147518dc5bca25f447bd0fb5359ac up to, but not including, f96b9f7c1676923bce871e728bb49c0dfa5013cc; 45a2966fd64147518dc5bca25f447bd0fb5359ac up to, but not including, 9a6c710f3bc10bc9cc23e1c080b53245b7f9d5b7; 45a2966fd64147518dc5bca25f447bd0fb5359ac up to, but not including, f87904c075515f3e1d8f4a7115869d3b914674fd; 5.15 | f96b9f7c1676923bce871e728bb49c0dfa5013cc, 9a6c710f3bc10bc9cc23e1c080b53245b7f9d5b7, f87904c075515f3e1d8f4a7115869d3b914674fd |
| Linux | Linux Kernel | 5.15 up to, but not including, 5.15.64; 5.16 up to, but not including, 5.19.6; 6.0 | 5.15.64, 5.19.6 |
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.
| 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: writeback: avoid use-after-free after removing device When a disk is removed, bdi_unregister gets called to stop further writeback and wait for associated delayed work to complete. However, wb_inode_writeback_end() may schedule bandwidth estimation dwork after this has completed, which can result in the timer attempting to access the just freed bdi_writeback. Fix this by checking if the bdi_writeback is alive, similar to when scheduling writeback work. Since this requires wb->work_lock, and wb_inode_writeback_end() may get called from interrupt, switch wb->work_lock to an irqsafe lock.
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
- 8.8 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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