CVE-2026-31581

Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: 6fire: fix use-after-free on disconnect In usb6fire_chip_abort(), the chip struct is allocated as the card's private data (via snd_card_new with sizeof(struct sfire_chip)). When snd_card_free_when_closed() is called and no file handles are open, the card and embedded chip are freed synchronously. The subsequent chip->card = NULL write then hits freed slab memory. Call trace: usb6fire_chip_abort sound/usb/6fire/chip.c:59 [inline] usb6fire_chip_disconnect+0x348/0x358 sound/usb/6fire/chip.c:182 usb_unbind_interface+0x1a8/0x88c drivers/usb/core/driver.c:458 ... hub_event+0x1a04/0x4518 drivers/usb/core/hub.c:5953 Fix by moving the card lifecycle out of usb6fire_chip_abort() and into usb6fire_chip_disconnect(). The card pointer is saved in a local before any teardown, snd_card_disconnect() is called first to prevent new opens, URBs are aborted while chip is still valid, and snd_card_free_when_closed() is called last so chip is never accessed after the card may be freed.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

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

Linux Kernel (Mainline)

Linux Kernel (Stable branches prior to specific patches)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * Conceptual Proof of Concept for CVE-2026-31581
 * This demonstrates the logic flaw leading to UAF.
 * Triggering this requires a USB 6fire device and specific timing.
 */

#include <linux/module.h>
#include <linux/usb.h>

// Simulating the vulnerable flow
void vulnerable_disconnect_logic(struct usb_interface *intf) {
    struct sfire_chip *chip = usb_get_intfdata(intf);
    
    // Step 1: Abort operations
    // usb6fire_chip_abort(chip);
    
    // Inside usb6fire_chip_abort (Vulnerable part):
    // If no file handles are open, snd_card_free_when_closed frees memory synchronously.
    if (chip && chip->card) {
        snd_card_free_when_closed(chip->card); // Chip memory is freed here
        
        // UAF: Writing to freed memory
        chip->card = NULL; // Vulnerability triggers here
    }
}

/*
 * Fix Implementation Logic:
 * 1. Save card pointer.
 * 2. Call snd_card_disconnect() first.
 * 3. Abort URBs.
 * 4. Call snd_card_free_when_closed() last.
 */

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31581
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31581
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31581/
[4] VulDB https://vuldb.com/cve/CVE-2026-31581
[5] https://git.kernel.org/stable/c/3dc20d1981d6a67d8184498a5da272942dde1e65
[6] https://git.kernel.org/stable/c/51f6532790b74ffdd6970bc848358a2838c1c185
[7] https://git.kernel.org/stable/c/af75b486f7e883e3422ece23c8d727e6815144a0
[8] https://git.kernel.org/stable/c/b9c826916fdce6419b94eb0cd8810fdac18c2386
[9] https://git.kernel.org/stable/c/d21e8a2af4869b5890b34e081d5aeadc93e9cd5c
[10] https://git.kernel.org/stable/c/e88354b381e2006de63d6b052ed7005c9a47d00e

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31581", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:32.797", "lastModified": "2026-04-27T20:28:08.840", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: 6fire: fix use-after-free on disconnect\n\nIn usb6fire_chip_abort(), the chip struct is allocated as the card's\nprivate data (via snd_card_new with sizeof(struct sfire_chip)). When\nsnd_card_free_when_closed() is called and no file handles are open, the\ncard and embedded chip are freed synchronously. The subsequent\nchip->card = NULL write then hits freed slab memory.\n\nCall trace:\n usb6fire_chip_abort sound/usb/6fire/chip.c:59 [inline]\n usb6fire_chip_disconnect+0x348/0x358 sound/usb/6fire/chip.c:182\n usb_unbind_interface+0x1a8/0x88c drivers/usb/core/driver.c:458\n ...\n hub_event+0x1a04/0x4518 drivers/usb/core/hub.c:5953\n\nFix by moving the card lifecycle out of usb6fire_chip_abort() and into\nusb6fire_chip_disconnect(). The card pointer is saved in a local\nbefore any teardown, snd_card_disconnect() is called first to prevent\nnew opens, URBs are aborted while chip is still valid, and\nsnd_card_free_when_closed() is called last so chip is never accessed\nafter the card may be freed."}], "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:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "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:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.6.136", "matchCriteriaId": "14109CEF-714B-4029-A318-97AA58A01833"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.12.83", "matchCriteriaId": "A8BAD957-8E20-401C-A129-DFF3655CA0B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/3dc20d1981d6a67d8184498a5da272942dde1e65", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/51f6532790b74ffdd6970bc848358a2838c1c185", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/af75b486f7e883e3422ece23c8d727e6815144a0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b9c826916fdce6419b94eb0cd8810fdac18c2386", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d21e8a2af4869b5890b34e081d5aeadc93e9cd5c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e88354b381e2006de63d6b052ed7005c9a47d00e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}