CVE-2026-31736

Description

In the Linux kernel, the following vulnerability has been resolved: net: ethernet: mtk_ppe: avoid NULL deref when gmac0 is disabled If the gmac0 is disabled, the precheck for a valid ingress device will cause a NULL pointer deref and crash the system. This happens because eth->netdev[0] will be NULL but the code will directly try to access netdev_ops. Instead of just checking for the first net_device, it must be checked if any of the mtk_eth net_devices is matching the netdev_ops of the ingress device.

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

cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* - VULNERABLE

Linux Kernel (Stable branches before commit 0b832aad33e6f160fda310f0306a6483d85e9d6e)

Linux Kernel (Stable branches before commit 5dff799c677152dde963c3917bacd9127b03e145)

Linux Kernel (Stable branches before commit 7b2380f0a0e374010c1a4a13203511b9dee5b166)

Linux Kernel (Stable branches before commit 976ff48c2ac6e6b25b01428c9d7997bcd0fb2949)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC Concept: Demonstration of the NULL pointer dereference logic
 * This snippet illustrates the vulnerable logic in mtk_ppe.c.
 * Exploitation requires a specific kernel configuration where gmac0 is disabled.
 */

#include <linux/netdevice.h>

// Simplified structure representation
struct mtk_eth {
    struct net_device *netdev[2]; // netdev[0] is NULL when gmac0 is disabled
};

void vulnerable_check(struct mtk_eth *eth, struct net_device *ingress_dev) {
    // Vulnerable logic: Directly accesses netdev[0] without checking if it is NULL
    if (eth->netdev[0]->netdev_ops == ingress_dev->netdev_ops) {
        // Do something
    }
}

void fixed_check(struct mtk_eth *eth, struct net_device *ingress_dev) {
    // Fixed logic: Check if netdev[0] is valid first
    int i;
    for (i = 0; i < 2; i++) {
        if (eth->netdev[i] && eth->netdev[i]->netdev_ops == ingress_dev->netdev_ops) {
            // Do something
            break;
        }
    }
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31736
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31736
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31736/
[4] VulDB https://vuldb.com/cve/CVE-2026-31736
[5] https://git.kernel.org/stable/c/0b832aad33e6f160fda310f0306a6483d85e9d6e
[6] https://git.kernel.org/stable/c/5dff799c677152dde963c3917bacd9127b03e145
[7] https://git.kernel.org/stable/c/7b2380f0a0e374010c1a4a13203511b9dee5b166
[8] https://git.kernel.org/stable/c/976ff48c2ac6e6b25b01428c9d7997bcd0fb2949

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31736", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:36.240", "lastModified": "2026-05-07T16:53:14.840", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ethernet: mtk_ppe: avoid NULL deref when gmac0 is disabled\n\nIf the gmac0 is disabled, the precheck for a valid ingress device will\ncause a NULL pointer deref and crash the system. This happens because\neth->netdev[0] will be NULL but the code will directly try to access\nnetdev_ops.\n\nInstead of just checking for the first net_device, it must be checked if\nany of the mtk_eth net_devices is matching the netdev_ops of the ingress\ndevice."}], "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-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.12.81", "matchCriteriaId": "41664AAE-F159-4875-BF5B-B86E659ADB8A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0b832aad33e6f160fda310f0306a6483d85e9d6e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5dff799c677152dde963c3917bacd9127b03e145", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7b2380f0a0e374010c1a4a13203511b9dee5b166", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/976ff48c2ac6e6b25b01428c9d7997bcd0fb2949", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}