Linux: Use After Free
CVE-2025-39871 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 24414bbcb37e1af95190af36c21ae51d497e1a9e, 0e95ee7f532b21206fe3f1c4054002b0d21e3b9c, dd7a7e43269711d757fc260b0bbdf7138f75de11 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 0.15% 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 24414bbcb37e1af95190af36c21ae51d497e1a9e or 0e95ee7f532b21206fe3f1c4054002b0d21e3b9c or dd7a7e43269711d757fc260b0bbdf7138f75de11 or da4fbc1488a4cec6748da685181ee4449a878dac, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.2 or 6.6.107 or 6.12.48 or 6.15, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 68ac5a01f635b3791196fd1c39bc48497252c36f up to, but not including, 24414bbcb37e1af95190af36c21ae51d497e1a9e; d2d05fd0fc95c4defed6f7b87550e20e8baa1d97 up to, but not including, 0e95ee7f532b21206fe3f1c4054002b0d21e3b9c; 21f9f5cd9a0c75084d4369ba0b8c4f695c41dea7 up to, but not including, dd7a7e43269711d757fc260b0bbdf7138f75de11; d5449ff1b04dfe9ed8e455769aa01e4c2ccf6805 up to, but not including, da4fbc1488a4cec6748da685181ee4449a878dac; d5449ff1b04dfe9ed8e455769aa01e4c2ccf6805 up to, but not including, f41c538881eec4dcf5961a242097d447f848cda6; 2b7a961cea0e5b65afda911f76d14fec5c98d024; 6.1.140 up to, but not including, 6.1.160; 6.6.92 up to, but not including, 6.6.107; and 3 more ranges | 24414bbcb37e1af95190af36c21ae51d497e1a9e, 0e95ee7f532b21206fe3f1c4054002b0d21e3b9c, dd7a7e43269711d757fc260b0bbdf7138f75de11, da4fbc1488a4cec6748da685181ee4449a878dac, f41c538881eec4dcf5961a242097d447f848cda6, 6.1.160 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 6.1.140 up to, but not including, 6.2; 6.6.92 up to, but not including, 6.6.107; 6.12.30 up to, but not including, 6.12.48; 6.14.8 up to, but not including, 6.15; 6.15.1 up to, but not including, 6.16.8; 6.15; 6.17 | 6.2, 6.6.107, 6.12.48, 6.15, 6.16.8 |
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: dmaengine: idxd: Remove improper idxd_free The call to idxd_free() introduces a duplicate put_device() leading to a reference count underflow: refcount_t: underflow; use-after-free. WARNING: CPU: 15 PID: 4428 at lib/refcount.c:28 refcount_warn_saturate+0xbe/0x110 ... Call Trace: <TASK> idxd_remove+0xe4/0x120 [idxd] pci_device_remove+0x3f/0xb0 device_release_driver_internal+0x197/0x200 driver_detach+0x48/0x90 bus_remove_driver+0x74/0xf0 pci_unregister_driver+0x2e/0xb0 idxd_exit_module+0x34/0x7a0 [idxd] __do_sys_delete_module.constprop.0+0x183/0x280 do_syscall_64+0x54/0xd70 entry_SYSCALL_64_after_hwframe+0x76/0x7e The idxd_unregister_devices() which is invoked at the very beginning of idxd_remove(), already takes care of the necessary put_device() through the following call path: idxd_unregister_devices() -> device_unregister() -> put_device() In addition, when CONFIG_DEBUG_KOBJECT_RELEASE is enabled, put_device() may trigger asynchronous cleanup via schedule_delayed_work(). If idxd_free() is called immediately after, it can result in a use-after-free. Remove the improper idxd_free() to avoid both the refcount underflow and potential memory corruption during module unload.
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
Other references
Recent Use After Free vulnerabilities
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