CVE-2026-31716

Description

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: validate rec->used in journal-replay file record check check_file_record() validates rec->total against the record size but never validates rec->used. The do_action() journal-replay handlers read rec->used from disk and use it to compute memmove lengths: DeleteAttribute: memmove(attr, ..., used - asize - roff) CreateAttribute: memmove(..., attr, used - roff) change_attr_size: memmove(..., used - PtrOffset(rec, next)) When rec->used is smaller than the offset of a validated attribute, or larger than the record size, these subtractions can underflow allowing us to copy huge amounts of memory in to a 4kb buffer, generally considered a bad idea overall. This requires a corrupted filesystem, which isn't a threat model the kernel really needs to worry about, but checking for such an obvious out-of-bounds value is good to keep things robust, especially on journal replay Fix this up by bounding rec->used correctly. This is much like commit b2bc7c44ed17 ("fs/ntfs3: Fix slab-out-of-bounds read in DeleteIndexEntryRoot") which checked different values in this same switch statement.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Configurations (Affected Products)

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

cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* - VULNERABLE

Linux Kernel (修复补丁提交前的版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

// Simulation of the vulnerable logic in fs/ntfs3/log.c
// This demonstrates the integer underflow issue.

#include <stdio.h>
#include <stdint.h>
#include <string.h>

struct FILE_RECORD {
    uint32_t total;
    uint32_t used;
    char data[4096];
};

void simulate_vulnerable_handler(struct FILE_RECORD *rec, uint32_t attr_offset) {
    // Vulnerable logic: rec->used is not validated against attr_offset
    // This mimics the 'DeleteAttribute' or 'CreateAttribute' logic
    uint32_t copy_len = rec->used - attr_offset;
    
    printf("Calculated copy length: %u\n", copy_len);
    
    // If rec->used is small (e.g., 10) and attr_offset is large (e.g., 100)
    // copy_len underflows to a very large value (e.g., 4294967206)
    // causing a massive copy into a small buffer.
    char buffer[100]; 
    // memmove(buffer, rec->data + attr_offset, copy_len); // This would crash
}

int main() {
    struct FILE_RECORD corrupted_rec;
    corrupted_rec.total = 4096;
    corrupted_rec.used = 10; // Malicious small value
    uint32_t attr_offset = 100; // Validated attribute offset
    
    printf("Simulating CVE-2026-31716 PoC...\n");
    simulate_vulnerable_handler(&corrupted_rec, attr_offset);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31716
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31716
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31716/
[4] VulDB https://vuldb.com/cve/CVE-2026-31716
[5] https://git.kernel.org/stable/c/0112e6279420d4005b3d57af36fb45c01b8d0116
[6] https://git.kernel.org/stable/c/0ca0485e4b2e837ebb6cbd4f2451aba665a03e4b
[7] https://git.kernel.org/stable/c/4b1613d7e2deda831a97e427d1ea586e50fe1be5
[8] https://git.kernel.org/stable/c/f79d0403ea20a81bc29105bba54fbcab54e8c403
[9] https://git.kernel.org/stable/c/f90b8a1798b750755a9e9aee66678f0a1820bbaf

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31716", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T14:16:21.743", "lastModified": "2026-05-06T21:10:23.290", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: validate rec->used in journal-replay file record check\n\ncheck_file_record() validates rec->total against the record size but\nnever validates rec->used. The do_action() journal-replay handlers read\nrec->used from disk and use it to compute memmove lengths:\n\n DeleteAttribute: memmove(attr, ..., used - asize - roff)\n CreateAttribute: memmove(..., attr, used - roff)\n change_attr_size: memmove(..., used - PtrOffset(rec, next))\n\nWhen rec->used is smaller than the offset of a validated attribute, or\nlarger than the record size, these subtractions can underflow allowing\nus to copy huge amounts of memory in to a 4kb buffer, generally\nconsidered a bad idea overall.\n\nThis requires a corrupted filesystem, which isn't a threat model the\nkernel really needs to worry about, but checking for such an obvious\nout-of-bounds value is good to keep things robust, especially on journal\nreplay\n\nFix this up by bounding rec->used correctly.\n\nThis is much like commit b2bc7c44ed17 (\"fs/ntfs3: Fix slab-out-of-bounds\nread in DeleteIndexEntryRoot\") which checked different values in this\nsame switch statement."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "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": "5.15", "versionEndExcluding": "6.6.136", "matchCriteriaId": "B1ABA9F0-A5C4-4CBE-92EC-33CA7D4F7634"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.84", "matchCriteriaId": "D4ECA0DE-AFF5-4688-B219-4CA2336CA5B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.25", "matchCriteriaId": "8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.0.2", "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*", "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0112e6279420d4005b3d57af36fb45c01b8d0116", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/0ca0485e4b2e837ebb6cbd4f2451aba665a03e4b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4b1613d7e2deda831a97e427d1ea586e50fe1be5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f79d0403ea20a81bc29105bba54fbcab54e8c403", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f90b8a1798b750755a9e9aee66678f0a1820bbaf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}