Linux: Use After Free
CVE-2022-48771 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 e8d092a62449dcfc73517ca43963d2b8f44d0516, 0008a0c78fc33a84e2212a7c04e6b21a36ca6f4d, 84b1259fe36ae0915f3d6ddcea6377779de48b82 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 0.21% 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 e8d092a62449dcfc73517ca43963d2b8f44d0516 or 0008a0c78fc33a84e2212a7c04e6b21a36ca6f4d or 84b1259fe36ae0915f3d6ddcea6377779de48b82 or ae2b20f27732fe92055d9e7b350abc5cdf3e2414, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.14.264 or 4.19.227 or 5.4.175 or 5.10.95, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, e8d092a62449dcfc73517ca43963d2b8f44d0516; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, 0008a0c78fc33a84e2212a7c04e6b21a36ca6f4d; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, 84b1259fe36ae0915f3d6ddcea6377779de48b82; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, ae2b20f27732fe92055d9e7b350abc5cdf3e2414; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, 6066977961fc6f437bc064f628cf9b0e4571c56c; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, 1d833b27fb708d6fdf5de9f6b3a8be4bd4321565; c906965dee22d5e95d0651759ba107b420212a9f up to, but not including, a0f90c8815706981c483a652a6aefca51a5e191c; 4.14 | e8d092a62449dcfc73517ca43963d2b8f44d0516, 0008a0c78fc33a84e2212a7c04e6b21a36ca6f4d, 84b1259fe36ae0915f3d6ddcea6377779de48b82, ae2b20f27732fe92055d9e7b350abc5cdf3e2414, 6066977961fc6f437bc064f628cf9b0e4571c56c, 1d833b27fb708d6fdf5de9f6b3a8be4bd4321565 |
| Linux | Linux Kernel | 4.14 up to, but not including, 4.14.264; 4.15 up to, but not including, 4.19.227; 4.20 up to, but not including, 5.4.175; 5.5 up to, but not including, 5.10.95; 5.11 up to, but not including, 5.15.18; 5.16 up to, but not including, 5.16.4; 5.17 | 4.14.264, 4.19.227, 5.4.175, 5.10.95, 5.15.18, 5.16.4 |
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: drm/vmwgfx: Fix stale file descriptors on failed usercopy A failing usercopy of the fence_rep object will lead to a stale entry in the file descriptor table as put_unused_fd() won't release it. This enables userland to refer to a dangling 'file' object through that still valid file descriptor, leading to all kinds of use-after-free exploitation scenarios. Fix this by deferring the call to fd_install() until after the usercopy has succeeded.
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
- git.kernel.org/stable/c/0008a0c78fc33a84e2212a7c04e6b21a36ca6f4d
- git.kernel.org/stable/c/1d833b27fb708d6fdf5de9f6b3a8be4bd4321565
- git.kernel.org/stable/c/6066977961fc6f437bc064f628cf9b0e4571c56c
- git.kernel.org/stable/c/84b1259fe36ae0915f3d6ddcea6377779de48b82
- git.kernel.org/stable/c/a0f90c8815706981c483a652a6aefca51a5e191c
- git.kernel.org/stable/c/ae2b20f27732fe92055d9e7b350abc5cdf3e2414
- git.kernel.org/stable/c/e8d092a62449dcfc73517ca43963d2b8f44d0516
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
- 8.8 High severity
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