Linux: Use After Free
CVE-2025-38620 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 c7c87046b41a9ef28ee7ac476c369da5b5228bc5, 765761851d89c772f482494d452e266795460278 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 c7c87046b41a9ef28ee7ac476c369da5b5228bc5 or 765761851d89c772f482494d452e266795460278, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | eb0570c7df23c2f32fe899fcdaf8fca9a5ecd51e up to, but not including, c7c87046b41a9ef28ee7ac476c369da5b5228bc5; eb0570c7df23c2f32fe899fcdaf8fca9a5ecd51e up to, but not including, 765761851d89c772f482494d452e266795460278; 6.16 | c7c87046b41a9ef28ee7ac476c369da5b5228bc5, 765761851d89c772f482494d452e266795460278 |
| Linux | Linux Kernel | 6.16 | 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.
Official description
In the Linux kernel, the following vulnerability has been resolved: zloop: fix KASAN use-after-free of tag set When a zoned loop device, or zloop device, is removed, KASAN enabled kernel reports "BUG KASAN use-after-free" in blk_mq_free_tag_set(). The BUG happens because zloop_ctl_remove() calls put_disk(), which invokes zloop_free_disk(). The zloop_free_disk() frees the memory allocated for the zlo pointer. However, after the memory is freed, zloop_ctl_remove() calls blk_mq_free_tag_set(&zlo->tag_set), which accesses the freed zlo. Hence the KASAN use-after-free. zloop_ctl_remove() put_disk(zlo->disk) put_device() kobject_put() ... zloop_free_disk() kvfree(zlo) blk_mq_free_tag_set(&zlo->tag_set) To avoid the BUG, move the call to blk_mq_free_tag_set(&zlo->tag_set) from zloop_ctl_remove() into zloop_free_disk(). This ensures that the tag_set is freed before the call to kvfree(zlo).
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
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.