CVE-2026-31748

Description

In the Linux kernel, the following vulnerability has been resolved: comedi: me_daq: Fix potential overrun of firmware buffer `me2600_xilinx_download()` loads the firmware that was requested by `request_firmware()`. It is possible for it to overrun the source buffer because it blindly trusts the file format. It reads a data stream length from the first 4 bytes into variable `file_length` and reads the data stream contents of length `file_length` from offset 16 onwards. Although it checks that the supplied firmware is at least 16 bytes long, it does not check that it is long enough to contain the data stream. Add a test to ensure that the supplied firmware is long enough to contain the header and the data stream. On failure, log an error and return `-EINVAL`.

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 (受影响版本，具体参考Git修复提交)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * Conceptual PoC for CVE-2026-31748
 * demonstrating the missing bounds check.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Mock structure for firmware
typedef struct {
    size_t size;
    char *data;
} firmware;

// Vulnerable function logic (simplified reproduction)
int vulnerable_firmware_load(firmware *fw) {
    // Check if firmware is at least 16 bytes
    if (fw->size < 16) {
        printf("Error: Firmware too small for header.\n");
        return -1;
    }

    // Read file_length from first 4 bytes (blind trust)
    unsigned int file_length = *(unsigned int *)(fw->data);
    printf("File Length from header: %u\n", file_length);

    // VULNERABILITY: Missing check for (fw->size >= 16 + file_length)
    // If file_length is huge (e.g., 0xFFFFFFFF), the loop below overruns the buffer
    if (fw->size < 16 + file_length) {
        printf("[Potential Exploit] Buffer Overrun detected!\n");
        // In the real kernel, this leads to OOB read/write
    }

    printf("Simulating data copy...\n");
    // This would crash or read OOB in real scenario
    return 0;
}

int main() {
    // Construct a malicious firmware: 20 bytes total, but claims 1000 bytes of data
    unsigned int fake_length = 1000;
    char malicious_data[20];
    memset(malicious_data, 0, 20);
    memcpy(malicious_data, &fake_length, 4); // Set length in header

    firmware fw;
    fw.size = 20; // Actual size is 20 (> 16, passes initial check)
    fw.data = malicious_data;

    printf("Triggering vulnerable function...\n");
    vulnerable_firmware_load(&fw);

    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31748
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31748
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31748/
[4] VulDB https://vuldb.com/cve/CVE-2026-31748
[5] https://git.kernel.org/stable/c/1bf8761eb59e94bf7b8c17b2a1ee48f14378b172
[6] https://git.kernel.org/stable/c/2fc25a4c2e055cd42ea39a1b42c89bfef70e0319
[7] https://git.kernel.org/stable/c/9f39fa07259eb342908e4aa0271dee038a8ce4f8
[8] https://git.kernel.org/stable/c/a47ae40339c1048f519df33ff8840731720f57cb
[9] https://git.kernel.org/stable/c/c16ac4e173a05011437a2d868f70cc415339065a
[10] https://git.kernel.org/stable/c/c8c607a77aab783f2e38cc2e0f24aa6c8f6d200b
[11] https://git.kernel.org/stable/c/cc797d4821c754c701d9714b58bea947e31dbbe0
[12] https://git.kernel.org/stable/c/f3f8ec00cfb8d8e826e30b1138a56355b88e9ba8

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31748", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:37.593", "lastModified": "2026-05-07T19:24:39.637", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: me_daq: Fix potential overrun of firmware buffer\n\n`me2600_xilinx_download()` loads the firmware that was requested by\n`request_firmware()`. It is possible for it to overrun the source\nbuffer because it blindly trusts the file format. It reads a data\nstream length from the first 4 bytes into variable `file_length` and\nreads the data stream contents of length `file_length` from offset 16\nonwards. Although it checks that the supplied firmware is at least 16\nbytes long, it does not check that it is long enough to contain the data\nstream.\n\nAdd a test to ensure that the supplied firmware is long enough to\ncontain the header and the data stream. On failure, log an error and\nreturn `-EINVAL`."}], "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-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "5.10.253", "matchCriteriaId": "0C1B1C38-DBED-4FC4-AE7D-B0A2622E224F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.168", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.134", "matchCriteriaId": "F56F925B-BAF8-4F4B-B62F-1496AF19A307"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.81", "matchCriteriaId": "6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC"}, {"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/1bf8761eb59e94bf7b8c17b2a1ee48f14378b172", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/2fc25a4c2e055cd42ea39a1b42c89bfef70e0319", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9f39fa07259eb342908e4aa0271dee038a8ce4f8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a47ae40339c1048f519df33ff8840731720f57cb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c16ac4e173a05011437a2d868f70cc415339065a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c8c607a77aab783f2e38cc2e0f24aa6c8f6d200b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch ... 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