Linux: Use After Free
CVE-2022-50329 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 1425f1bb5df5239021fd09ebc2a5e8070e705d36, 7949b0df3dd9f4817ed4a4e989fa9ee81df6205f, cfe5b38c37720313eff0dec5517442c7ab3c9a20 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 0.17% 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 1425f1bb5df5239021fd09ebc2a5e8070e705d36 or 7949b0df3dd9f4817ed4a4e989fa9ee81df6205f or cfe5b38c37720313eff0dec5517442c7ab3c9a20 or 1ed959fef5b1c6f1a7a3fbea543698c30ebd6678, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 5533742c7cb1bc9b1f0bf401cc397d44a3a9e07a up to, but not including, 1425f1bb5df5239021fd09ebc2a5e8070e705d36; 094f3d9314d67691cb21ba091c1b528f6e3c4893 up to, but not including, 7949b0df3dd9f4817ed4a4e989fa9ee81df6205f; b22fd72bfebda3956efc4431b60ddfc0a51e03e0 up to, but not including, cfe5b38c37720313eff0dec5517442c7ab3c9a20; 761564d93c8265f65543acf0a576b32d66bfa26a up to, but not including, 1ed959fef5b1c6f1a7a3fbea543698c30ebd6678; 64dc8c732f5c2b406cc752e6aaa1bd5471159cab up to, but not including, 246cf66e300b76099b5dbd3fdd39e9a5dbc53f02; 5.15.86 up to, but not including, 5.15.87; 6.0.16 up to, but not including, 6.0.17; 6.1.2 up to, but not including, 6.1.3 | 1425f1bb5df5239021fd09ebc2a5e8070e705d36, 7949b0df3dd9f4817ed4a4e989fa9ee81df6205f, cfe5b38c37720313eff0dec5517442c7ab3c9a20, 1ed959fef5b1c6f1a7a3fbea543698c30ebd6678, 246cf66e300b76099b5dbd3fdd39e9a5dbc53f02, 5.15.87 |
| Linux | Linux Kernel | 5.15.86; 6.0.16; 6.1.2; 6.2 | Not stated |
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: block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq Commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'") will access 'bic->bfqq' in bic_set_bfqq(), however, bfq_exit_icq_bfqq() can free bfqq first, and then call bic_set_bfqq(), which will cause uaf. Fix the problem by moving bfq_exit_bfqq() behind bic_set_bfqq().
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/1425f1bb5df5239021fd09ebc2a5e8070e705d36
- git.kernel.org/stable/c/1ed959fef5b1c6f1a7a3fbea543698c30ebd6678
- git.kernel.org/stable/c/246cf66e300b76099b5dbd3fdd39e9a5dbc53f02
- git.kernel.org/stable/c/7949b0df3dd9f4817ed4a4e989fa9ee81df6205f
- git.kernel.org/stable/c/cfe5b38c37720313eff0dec5517442c7ab3c9a20
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
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