Linux: Use After Free
CVE-2022-49626 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 3199e34912d84cdfb8a93a984c5ae5c73fb13e84, c9e75bb22a26e391f189f5a5133dd63dcb57fdaa, 9c854ae512b89229aeee93849e9bd4c115b37909 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 0.28% 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 3199e34912d84cdfb8a93a984c5ae5c73fb13e84 or c9e75bb22a26e391f189f5a5133dd63dcb57fdaa or 9c854ae512b89229aeee93849e9bd4c115b37909 or bcad880865bfb421885364b1f0c7351280fe2b97, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.9.324 or 4.14.289 or 4.19.253 or 5.4.207, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, 3199e34912d84cdfb8a93a984c5ae5c73fb13e84; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, c9e75bb22a26e391f189f5a5133dd63dcb57fdaa; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, 9c854ae512b89229aeee93849e9bd4c115b37909; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, bcad880865bfb421885364b1f0c7351280fe2b97; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, c2240500817b3b4b996cdf2a461a3a5679f49b94; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, 58d93e9d160c0de6d867c7eb4c2206671a351eb1; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, e435c4aeeaa073091f7f3b7735af2ef5c97d63f2; 3c5eb87605e85146a78de589b5070a37862425db up to, but not including, ebe41da5d47ac0fff877e57bd14c54dccf168827; and 1 more ranges | 3199e34912d84cdfb8a93a984c5ae5c73fb13e84, c9e75bb22a26e391f189f5a5133dd63dcb57fdaa, 9c854ae512b89229aeee93849e9bd4c115b37909, bcad880865bfb421885364b1f0c7351280fe2b97, c2240500817b3b4b996cdf2a461a3a5679f49b94, 58d93e9d160c0de6d867c7eb4c2206671a351eb1 |
| Linux | Linux Kernel | 4.2 up to, but not including, 4.9.324; 4.10 up to, but not including, 4.14.289; 4.15 up to, but not including, 4.19.253; 4.20 up to, but not including, 5.4.207; 5.5 up to, but not including, 5.10.132; 5.11 up to, but not including, 5.15.56; 5.16 up to, but not including, 5.18.13; 5.19 | 4.9.324, 4.14.289, 4.19.253, 5.4.207, 5.10.132, 5.15.56 |
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: sfc: fix use after free when disabling sriov Use after free is detected by kfence when disabling sriov. What was read after being freed was vf->pci_dev: it was freed from pci_disable_sriov and later read in efx_ef10_sriov_free_vf_vports, called from efx_ef10_sriov_free_vf_vswitching. Set the pointer to NULL at release time to not trying to read it later. Reproducer and dmesg log (note that kfence doesn't detect it every time): $ echo 1 > /sys/class/net/enp65s0f0np0/device/sriov_numvfs $ echo 0 > /sys/class/net/enp65s0f0np0/device/sriov_numvfs BUG: KFENCE: use-after-free read in efx_ef10_sriov_free_vf_vswitching+0x82/0x170 [sfc] Use-after-free read at 0x00000000ff3c1ba5 (in kfence-#224): efx_ef10_sriov_free_vf_vswitching+0x82/0x170 [sfc] efx_ef10_pci_sriov_disable+0x38/0x70 [sfc] efx_pci_sriov_configure+0x24/0x40 [sfc] sriov_numvfs_store+0xfe/0x140 kernfs_fop_write_iter+0x11c/0x1b0 new_sync_write+0x11f/0x1b0 vfs_write+0x1eb/0x280 ksys_write+0x5f/0xe0 do_syscall_64+0x5c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae kfence-#224: 0x00000000edb8ef95-0x00000000671f5ce1, size=2792, cache=kmalloc-4k allocated by task 6771 on cpu 10 at 3137.860196s: pci_alloc_dev+0x21/0x60 pci_iov_add_virtfn+0x2a2/0x320 sriov_enable+0x212/0x3e0 efx_ef10_sriov_configure+0x67/0x80 [sfc] efx_pci_sriov_configure+0x24/0x40 [sfc] sriov_numvfs_store+0xba/0x140 kernfs_fop_write_iter+0x11c/0x1b0 new_sync_write+0x11f/0x1b0 vfs_write+0x1eb/0x280 ksys_write+0x5f/0xe0 do_syscall_64+0x5c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae freed by task 6771 on cpu 12 at 3170.991309s: device_release+0x34/0x90 kobject_cleanup+0x3a/0x130 pci_iov_remove_virtfn+0xd9/0x120 sriov_disable+0x30/0xe0 efx_ef10_pci_sriov_disable+0x57/0x70 [sfc] efx_pci_sriov_configure+0x24/0x40 [sfc] sriov_numvfs_store+0xfe/0x140 kernfs_fop_write_iter+0x11c/0x1b0 new_sync_write+0x11f/0x1b0 vfs_write+0x1eb/0x280 ksys_write+0x5f/0xe0 do_syscall_64+0x5c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae
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
- git.kernel.org/stable/c/3199e34912d84cdfb8a93a984c5ae5c73fb13e84
- git.kernel.org/stable/c/58d93e9d160c0de6d867c7eb4c2206671a351eb1
- git.kernel.org/stable/c/9c854ae512b89229aeee93849e9bd4c115b37909
- git.kernel.org/stable/c/bcad880865bfb421885364b1f0c7351280fe2b97
- git.kernel.org/stable/c/c2240500817b3b4b996cdf2a461a3a5679f49b94
- git.kernel.org/stable/c/c9e75bb22a26e391f189f5a5133dd63dcb57fdaa
- git.kernel.org/stable/c/e435c4aeeaa073091f7f3b7735af2ef5c97d63f2
- git.kernel.org/stable/c/ebe41da5d47ac0fff877e57bd14c54dccf168827
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
Spotted an error? Tell us.