Linux: Use After Free
CVE-2026-31530 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 b1f62588ab1be6c9535d74348003c86b47ec4abd, d216a4bd138eb57cc4ae7c43b2f709e3482af7e2, 2c32141462045cf93d54a5146a0ba572b83533dd 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 0.16% 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 b1f62588ab1be6c9535d74348003c86b47ec4abd or d216a4bd138eb57cc4ae7c43b2f709e3482af7e2 or 2c32141462045cf93d54a5146a0ba572b83533dd or f7dc6f381a1e5f068333f1faa9265d6af1df4235, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.80 or 6.18.21 or 6.19.11, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2345df54249c6fb7779e2a72b427ee79ed3eaad5 up to, but not including, b1f62588ab1be6c9535d74348003c86b47ec4abd; 2345df54249c6fb7779e2a72b427ee79ed3eaad5 up to, but not including, d216a4bd138eb57cc4ae7c43b2f709e3482af7e2; 2345df54249c6fb7779e2a72b427ee79ed3eaad5 up to, but not including, 2c32141462045cf93d54a5146a0ba572b83533dd; 2345df54249c6fb7779e2a72b427ee79ed3eaad5 up to, but not including, f7dc6f381a1e5f068333f1faa9265d6af1df4235; 2345df54249c6fb7779e2a72b427ee79ed3eaad5 up to, but not including, 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4; 6.3 | b1f62588ab1be6c9535d74348003c86b47ec4abd, d216a4bd138eb57cc4ae7c43b2f709e3482af7e2, 2c32141462045cf93d54a5146a0ba572b83533dd, f7dc6f381a1e5f068333f1faa9265d6af1df4235, 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4 |
| Linux | Linux Kernel | 6.3 up to, but not including, 6.12.80; 6.13 up to, but not including, 6.18.21; 6.19 up to, but not including, 6.19.11; 7.0 | 6.12.80, 6.18.21, 6.19.11 |
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: cxl/port: Fix use after free of parent_port in cxl_detach_ep() cxl_detach_ep() is called during bottom-up removal when all CXL memory devices beneath a switch port have been removed. For each port in the hierarchy it locks both the port and its parent, removes the endpoint, and if the port is now empty, marks it dead and unregisters the port by calling delete_switch_port(). There are two places during this work where the parent_port may be used after freeing: First, a concurrent detach may have already processed a port by the time a second worker finds it via bus_find_device(). Without pinning parent_port, it may already be freed when we discover port->dead and attempt to unlock the parent_port. In a production kernel that's a silent memory corruption, with lock debug, it looks like this: []DEBUG_LOCKS_WARN_ON(__owner_task(owner) != get_current()) []WARNING: kernel/locking/mutex.c:949 at __mutex_unlock_slowpath+0x1ee/0x310 []Call Trace: []mutex_unlock+0xd/0x20 []cxl_detach_ep+0x180/0x400 [cxl_core] []devm_action_release+0x10/0x20 []devres_release_all+0xa8/0xe0 []device_unbind_cleanup+0xd/0xa0 []really_probe+0x1a6/0x3e0 Second, delete_switch_port() releases three devm actions registered against parent_port. The last of those is unregister_port() and it calls device_unregister() on the child port, which can cascade. If parent_port is now also empty the device core may unregister and free it too. So by the time delete_switch_port() returns, parent_port may be free, and the subsequent device_unlock(&parent_port->dev) operates on freed memory. The kernel log looks same as above, with a different offset in cxl_detach_ep(). Both of these issues stem from the absence of a lifetime guarantee between a child port and its parent port. Establish a lifetime rule for ports: child ports hold a reference to their parent device until release. Take the reference when the port is allocated and drop it when released. This ensures the parent is valid for the full lifetime of the child and eliminates the use after free window in cxl_detach_ep(). This is easily reproduced with a reload of cxl_acpi in QEMU with CXL devices present.
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
Other references
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