Linux: Use After Free
CVE-2022-49390 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 78933cbc143b82d02330e00900d2fd08f2682f4e, d130282179aa6051449ac8f8df1115769998a665, 196a888ca6571deb344468e1d7138e3273206335 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 78933cbc143b82d02330e00900d2fd08f2682f4e or d130282179aa6051449ac8f8df1115769998a665 or 196a888ca6571deb344468e1d7138e3273206335 or 4.15, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.15 or 4.20 or 5.17.15 or 5.18.3, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2bce1ebed17da54c65042ec2b962e3234bad5b47 up to, but not including, 78933cbc143b82d02330e00900d2fd08f2682f4e; 2bce1ebed17da54c65042ec2b962e3234bad5b47 up to, but not including, d130282179aa6051449ac8f8df1115769998a665; 2bce1ebed17da54c65042ec2b962e3234bad5b47 up to, but not including, 196a888ca6571deb344468e1d7138e3273206335; 1861904a6092ed411203c6a02c75bfc45b27cc3c; 3a2675a2d97a68332fa5c33043038bfeb31455a8; b0add6db3d5ec4561cab257358871a9d3df7f0a3; 4.14.154 up to, but not including, 4.15; 4.19.84 up to, but not including, 4.20; and 2 more ranges | 78933cbc143b82d02330e00900d2fd08f2682f4e, d130282179aa6051449ac8f8df1115769998a665, 196a888ca6571deb344468e1d7138e3273206335, 4.15, 4.20, 5.4 |
| Linux | Linux Kernel | 4.14.154 up to, but not including, 4.15; 4.19.84 up to, but not including, 4.20; 5.3.11 up to, but not including, 5.17.15; 5.18 up to, but not including, 5.18.3 | 4.15, 4.20, 5.17.15, 5.18.3 |
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 CISA (ADP).
Official description
In the Linux kernel, the following vulnerability has been resolved: macsec: fix UAF bug for real_dev Create a new macsec device but not get reference to real_dev. That can not ensure that real_dev is freed after macsec. That will trigger the UAF bug for real_dev as following: ================================================================== BUG: KASAN: use-after-free in macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662 Call Trace: ... macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662 dev_get_iflink+0x73/0xe0 net/core/dev.c:637 default_operstate net/core/link_watch.c:42 [inline] rfc2863_policy+0x233/0x2d0 net/core/link_watch.c:54 linkwatch_do_dev+0x2a/0x150 net/core/link_watch.c:161 Allocated by task 22209: ... alloc_netdev_mqs+0x98/0x1100 net/core/dev.c:10549 rtnl_create_link+0x9d7/0xc00 net/core/rtnetlink.c:3235 veth_newlink+0x20e/0xa90 drivers/net/veth.c:1748 Freed by task 8: ... kfree+0xd6/0x4d0 mm/slub.c:4552 kvfree+0x42/0x50 mm/util.c:615 device_release+0x9f/0x240 drivers/base/core.c:2229 kobject_cleanup lib/kobject.c:673 [inline] kobject_release lib/kobject.c:704 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1c8/0x540 lib/kobject.c:721 netdev_run_todo+0x72e/0x10b0 net/core/dev.c:10327 After commit faab39f63c1f ("net: allow out-of-order netdev unregistration") and commit e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev"), we can add dev_hold_track() in macsec_dev_init() and dev_put_track() in macsec_free_netdev() to fix the problem.
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: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
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