Linux: Use After Free
CVE-2024-49854 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 63a07379fdb6c72450cb05294461c6016b8b7726, de0456460f2abf921e356ed2bd8da87a376680bd, 0780451f03bf518bc032a7c584de8f92e2d39d7f 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 63a07379fdb6c72450cb05294461c6016b8b7726 or de0456460f2abf921e356ed2bd8da87a376680bd or 0780451f03bf518bc032a7c584de8f92e2d39d7f or 0b8bda0ff17156cd3f60944527c9d8c9f99f1583, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.168 or 6.1.113 or 6.6.54 or 6.10.13, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e0c20d88b7dce85d2703bb6ba77bf359959675cd up to, but not including, 63a07379fdb6c72450cb05294461c6016b8b7726; de6c5e3a456019d2182e345730e59721714fa0b5 up to, but not including, de0456460f2abf921e356ed2bd8da87a376680bd; 19f3bec2ac4be329b9bd12b18a989b867618d2d8 up to, but not including, 0780451f03bf518bc032a7c584de8f92e2d39d7f; 13b3d0e8cb121f99b11918a0d4bcc1ce4647d352 up to, but not including, 0b8bda0ff17156cd3f60944527c9d8c9f99f1583; 4780f50ea50cfe8e89fc3747bf3dd155488433bb up to, but not including, cae58d19121a70329cf971359e2518c93fec04fe; 42c306ed723321af4003b2a41bb73728cab54f85 up to, but not including, 1ba0403ac6447f2d63914fb760c44a3b19c44eaf; 9e813033594b141f61ff0ef0cfaaef292564b041; 3a5f45a4ad4e1fd36b0a998eef03d76a4f02a2a8; and 4 more ranges | 63a07379fdb6c72450cb05294461c6016b8b7726, de0456460f2abf921e356ed2bd8da87a376680bd, 0780451f03bf518bc032a7c584de8f92e2d39d7f, 0b8bda0ff17156cd3f60944527c9d8c9f99f1583, cae58d19121a70329cf971359e2518c93fec04fe, 1ba0403ac6447f2d63914fb760c44a3b19c44eaf |
| Linux | Linux Kernel | 5.10.227 up to, but not including, 5.15.168; 5.16 up to, but not including, 6.1.113; 6.2 up to, but not including, 6.6.54; 6.7 up to, but not including, 6.10.13; 6.11 up to, but not including, 6.11.2 | 5.15.168, 6.1.113, 6.6.54, 6.10.13, 6.11.2 |
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 accessing waker_bfqq after splitting After commit 42c306ed7233 ("block, bfq: don't break merge chain in bfq_split_bfqq()"), if the current procress is the last holder of bfqq, the bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and then access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq may in the merge chain of bfqq, hence just recored waker_bfqq is still not safe. Fix the problem by adding a helper bfq_waker_bfqq() to check if bfqq->waker_bfqq is in the merge chain, and current procress is the only holder.
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/0780451f03bf518bc032a7c584de8f92e2d39d7f
- git.kernel.org/stable/c/0b8bda0ff17156cd3f60944527c9d8c9f99f1583
- git.kernel.org/stable/c/1ba0403ac6447f2d63914fb760c44a3b19c44eaf
- git.kernel.org/stable/c/63a07379fdb6c72450cb05294461c6016b8b7726
- git.kernel.org/stable/c/cae58d19121a70329cf971359e2518c93fec04fe
- git.kernel.org/stable/c/de0456460f2abf921e356ed2bd8da87a376680bd
Other references
Recent Use After Free vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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