Linux: Use After Free
CVE-2026-31500 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 7e041d0aad1d4d43d921ace052e04f4e2cacaed3, 5f84e845648dfa86e42de5487f1a774b42f0444d, e10a4cb72468686ffbe8bb2b0520e37f6be1a0c5 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 0.13% 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 7e041d0aad1d4d43d921ace052e04f4e2cacaed3 or 5f84e845648dfa86e42de5487f1a774b42f0444d or e10a4cb72468686ffbe8bb2b0520e37f6be1a0c5 or 66696648af477dc87859e5e4b607112f5f29d010, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.131 or 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 | 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, 7e041d0aad1d4d43d921ace052e04f4e2cacaed3; 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, 5f84e845648dfa86e42de5487f1a774b42f0444d; 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, e10a4cb72468686ffbe8bb2b0520e37f6be1a0c5; 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, 66696648af477dc87859e5e4b607112f5f29d010; 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, f7d84737663ad4a120d2d8ef1561a4df91282c2e; 973bb97e5aee56edddaae3d5c96877101ad509c0 up to, but not including, 94d8e6fe5d0818e9300e514e095a200bd5ff93ae; 4.3 | 7e041d0aad1d4d43d921ace052e04f4e2cacaed3, 5f84e845648dfa86e42de5487f1a774b42f0444d, e10a4cb72468686ffbe8bb2b0520e37f6be1a0c5, 66696648af477dc87859e5e4b607112f5f29d010, f7d84737663ad4a120d2d8ef1561a4df91282c2e, 94d8e6fe5d0818e9300e514e095a200bd5ff93ae |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Linux | Linux Kernel | 4.3.1 up to, but not including, 6.6.131; 6.7 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; 4.3; 7.0 | 6.6.131, 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: Bluetooth: btintel: serialize btintel_hw_error() with hci_req_sync_lock btintel_hw_error() issues two __hci_cmd_sync() calls (HCI_OP_RESET and Intel exception-info retrieval) without holding hci_req_sync_lock(). This lets it race against hci_dev_do_close() -> btintel_shutdown_combined(), which also runs __hci_cmd_sync() under the same lock. When both paths manipulate hdev->req_status/req_rsp concurrently, the close path may free the response skb first, and the still-running hw_error path hits a slab-use-after-free in kfree_skb(). Wrap the whole recovery sequence in hci_req_sync_lock/unlock so it is serialized with every other synchronous HCI command issuer. Below is the data race report and the kasan report: BUG: data-race in __hci_cmd_sync_sk / btintel_shutdown_combined read of hdev->req_rsp at net/bluetooth/hci_sync.c:199 by task kworker/u17:1/83: __hci_cmd_sync_sk+0x12f2/0x1c30 net/bluetooth/hci_sync.c:200 __hci_cmd_sync+0x55/0x80 net/bluetooth/hci_sync.c:223 btintel_hw_error+0x114/0x670 drivers/bluetooth/btintel.c:254 hci_error_reset+0x348/0xa30 net/bluetooth/hci_core.c:1030 write/free by task ioctl/22580: btintel_shutdown_combined+0xd0/0x360 drivers/bluetooth/btintel.c:3648 hci_dev_close_sync+0x9ae/0x2c10 net/bluetooth/hci_sync.c:5246 hci_dev_do_close+0x232/0x460 net/bluetooth/hci_core.c:526 BUG: KASAN: slab-use-after-free in sk_skb_reason_drop+0x43/0x380 net/core/skbuff.c:1202 Read of size 4 at addr ffff888144a738dc by task kworker/u17:1/83: __hci_cmd_sync_sk+0x12f2/0x1c30 net/bluetooth/hci_sync.c:200 __hci_cmd_sync+0x55/0x80 net/bluetooth/hci_sync.c:223 btintel_hw_error+0x186/0x670 drivers/bluetooth/btintel.c:260
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/5f84e845648dfa86e42de5487f1a774b42f0444d
- git.kernel.org/stable/c/66696648af477dc87859e5e4b607112f5f29d010
- git.kernel.org/stable/c/94d8e6fe5d0818e9300e514e095a200bd5ff93ae
- git.kernel.org/stable/c/e10a4cb72468686ffbe8bb2b0520e37f6be1a0c5
- git.kernel.org/stable/c/f7d84737663ad4a120d2d8ef1561a4df91282c2e
Other references
Recent Use After Free vulnerabilities
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