CVE-2026-23461

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user After commit ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del"), l2cap_conn_del() uses conn->lock to protect access to conn->users. However, l2cap_register_user() and l2cap_unregister_user() don't use conn->lock, creating a race condition where these functions can access conn->users and conn->hchan concurrently with l2cap_conn_del(). This can lead to use-after-free and list corruption bugs, as reported by syzbot. Fix this by changing l2cap_register_user() and l2cap_unregister_user() to use conn->lock instead of hci_dev_lock(), ensuring consistent locking for the l2cap_conn structure.

CVSS Details

CVSS Score

8.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel (主要版本 < 6.8, 具体取决于发行版回溯情况)

Linux Kernel stable branches before commit da3000cbe4851458a22be38bb18c0689c39fdd5f

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

/*
 * Conceptual PoC for CVE-2026-23461
 * Demonstrating the race condition between l2cap_conn_del and l2cap_unregister_user.
 * This code is for educational analysis purposes only.
 */

#include <linux/module.h>
#include <linux/kthread.h>
#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/l2cap.h>

static struct l2cap_conn *target_conn;

// Thread 1: Simulates l2cap_conn_del path (holds conn->lock)
static int thread_delete_conn(void *data) {
    while (!kthread_should_stop()) {
        if (target_conn) {
            mutex_lock(&target_conn->lock);
            // Simulate deletion logic
            // Freeing resources without proper synchronization check
            if (target_conn->hchan)
                kfree(target_conn->hchan); // Potential free
            target_conn->hchan = NULL;
            mutex_unlock(&target_conn->lock);
        }
    }
    return 0;
}

// Thread 2: Simulates l2cap_unregister_user path (holds hci_dev_lock)
static int thread_unregister_user(void *data) {
    struct hci_dev *hdev = NULL;
    while (!kthread_should_stop()) {
        if (target_conn) {
            // Vulnerable: Uses wrong lock
            if (target_conn->hcon)
                hdev = target_conn->hcon->hdev;
            
            if (hdev) {
                hci_dev_lock(hdev);
                // Race: Accessing hchan which might be freed by Thread 1
                if (target_conn->hchan) {
                    printk(KERN_INFO "Accessing hchan: %p\n", target_conn->hchan);
                    // Use-After-Free occurs here
                }
                hci_dev_unlock(hdev);
            }
        }
    }
    return 0;
}

static int __init poc_init(void) {
    // Setup threads to race against each other
    // Requires a valid Bluetooth connection context to fully trigger
    return 0;
}

module_init(poc_init);

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23461
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23461
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23461/
[4] VulDB https://vuldb.com/cve/CVE-2026-23461
[5] https://git.kernel.org/stable/c/11a87dd5df428a4b79a84d2790cac7f3c73f1f0d
[6] https://git.kernel.org/stable/c/71030f3b3015a412133a805ff47970cdcf30c2b8
[7] https://git.kernel.org/stable/c/752a6c9596dd25efd6978a73ff21f3b592668f4a
[8] https://git.kernel.org/stable/c/c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf
[9] https://git.kernel.org/stable/c/da3000cbe4851458a22be38bb18c0689c39fdd5f

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23461", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-03T16:16:33.140", "lastModified": "2026-05-20T15:30:09.390", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user\n\nAfter commit ab4eedb790ca (\"Bluetooth: L2CAP: Fix corrupted list in\nhci_chan_del\"), l2cap_conn_del() uses conn->lock to protect access to\nconn->users. However, l2cap_register_user() and l2cap_unregister_user()\ndon't use conn->lock, creating a race condition where these functions can\naccess conn->users and conn->hchan concurrently with l2cap_conn_del().\n\nThis can lead to use-after-free and list corruption bugs, as reported\nby syzbot.\n\nFix this by changing l2cap_register_user() and l2cap_unregister_user()\nto use conn->lock instead of hci_dev_lock(), ensuring consistent locking\nfor the l2cap_conn structure."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.84", "versionEndExcluding": "6.6.130", "matchCriteriaId": "A87F64C1-AF3B-48DC-89AD-A8C7069BFBA8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.20", "versionEndExcluding": "6.12.78", "matchCriteriaId": "EDA52060-BD07-4881-B1B9-27DD1F069333"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13.8", "versionEndExcluding": "6.14", "matchCriteriaId": "366CEEDE-ED7E-4CD5-A00F-927D6C249DFD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14.1", "versionEndExcluding": "6.18.20", "matchCriteriaId": "BD54E28E-E5DD-4B1B-9B3C-D90CA91313C7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.10", "matchCriteriaId": "96D34333-38BE-4414-9E79-6EB764329581"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:-:*:*:*:*:*:*", "matchCriteriaId": "7DE421BA-0600-4401-A175-73CAB6A6FB4E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc3:*:*:*:*:*:*", "matchCriteriaId": "66619FB8-0AAF-4166-B2CF-67B24143261D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc4:*:*:*:*:*:*", "matchCriteriaId": "D3D6550E-6679-4560-902D-AF52DCFE905B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc5:*:*:*:*:*:*", "matchCriteriaId": "45B90F6B-BEC7-4D4E-883A-9DBADE021750"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc6:*:*:*:*:*:*", "matchCriteriaId": "1759FFB7-531C-41B1-9AE1-FD3D80E0D920"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc7:*:*:*:*:*:*", "matchCriteriaId": "AD948719-8628-4421-A340-1066314BBD4A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/11a87dd5df428a4b79a84d2790cac7f3c73f1f0d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/71030f3b3015a412133a805ff47970cdcf30c2b8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/752a6c9596dd25efd6978a73ff21f3b592668f4a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c22a5e659959eb77c2fbb58a5adfaf3c3dab7abf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/da3000cbe4851458a22be38bb18c0689c39fdd5f", "source": "416baaa9-dc9f-4396-8d5f-8c0 ... 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