CVE-2026-31780

Description

In the Linux kernel, the following vulnerability has been resolved: wifi: wilc1000: fix u8 overflow in SSID scan buffer size calculation The variable valuesize is declared as u8 but accumulates the total length of all SSIDs to scan. Each SSID contributes up to 33 bytes (IEEE80211_MAX_SSID_LEN + 1), and with WILC_MAX_NUM_PROBED_SSID (10) SSIDs the total can reach 330, which wraps around to 74 when stored in a u8. This causes kmalloc to allocate only 75 bytes while the subsequent memcpy writes up to 331 bytes into the buffer, resulting in a 256-byte heap buffer overflow. Widen valuesize from u8 to u32 to accommodate the full range.

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 (wilc1000 driver versions prior to fix)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC Concept for CVE-2026-31780
 * This code demonstrates the logic error causing the overflow.
 * Compile: gcc -o poc poc.c
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

#define WILC_MAX_NUM_PROBED_SSID 10
#define IEEE80211_MAX_SSID_LEN 32

// Vulnerable logic simulation
void simulate_vulnerability() {
    uint8_t valuesize = 0; // Vulnerable type u8
    int total_ssid_len = WILC_MAX_NUM_PROBED_SSID * (IEEE80211_MAX_SSID_LEN + 1);

    printf("[+] Simulating SSID size calculation...\n");
    
    for (int i = 0; i < WILC_MAX_NUM_PROBED_SSID; i++) {
        valuesize += (IEEE80211_MAX_SSID_LEN + 1);
    }

    printf("[+] Calculated size (u8): %d\n", valuesize);
    printf("[+] Actual required size: %d\n", total_ssid_len);

    if (valuesize < total_ssid_len) {
        printf("[!] Integer overflow detected! Allocating %d bytes but writing %d bytes.\n", valuesize, total_ssid_len);
        
        // Simulating the kmalloc and memcpy behavior
        char *buffer = (char *)malloc(valuesize + 1);
        if (buffer) {
            char dummy_data[400]; // Source data larger than buffer
            memset(dummy_data, 'A', sizeof(dummy_data));
            
            // This would cause heap overflow in the kernel
            // memcpy(buffer, dummy_data, total_ssid_len);
            printf("[!] In Kernel: memcpy(dst, src, %d) overflows buffer of size %d\n", total_ssid_len, valuesize);
            free(buffer);
        }
    }
}

int main() {
    simulate_vulnerability();
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31780
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31780
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31780/
[4] VulDB https://vuldb.com/cve/CVE-2026-31780
[5] https://git.kernel.org/stable/c/0c7f21d8bd2f93998b72b7a7f93152336aeca4dd
[6] https://git.kernel.org/stable/c/34a23fd9ddd683a03c7e8cc0ceded3e59e354b99
[7] https://git.kernel.org/stable/c/549f02d8ec94d39092ab6d9b103d0d6783a4b024
[8] https://git.kernel.org/stable/c/9907ac9b9a18b92fc34b9e4cb9e10f208dc1d3f7
[9] https://git.kernel.org/stable/c/bfbddeadd4779651403035ee177ae2f22f9f5521
[10] https://git.kernel.org/stable/c/c97b2a00059608592ad0d86fbb813a4f8cf9464b
[11] https://git.kernel.org/stable/c/d049e56b1739101d1c4d81deedb269c52a8dbba0
[12] https://git.kernel.org/stable/c/d8388614de613c28eeb659c10115060a83739924

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31780", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:41.453", "lastModified": "2026-05-11T20:54:09.280", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: wilc1000: fix u8 overflow in SSID scan buffer size calculation\n\nThe variable valuesize is declared as u8 but accumulates the total\nlength of all SSIDs to scan. Each SSID contributes up to 33 bytes\n(IEEE80211_MAX_SSID_LEN + 1), and with WILC_MAX_NUM_PROBED_SSID (10)\nSSIDs the total can reach 330, which wraps around to 74 when stored\nin a u8.\n\nThis causes kmalloc to allocate only 75 bytes while the subsequent\nmemcpy writes up to 331 bytes into the buffer, resulting in a 256-byte\nheap buffer overflow.\n\nWiden valuesize from u8 to u32 to accommodate the full range."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "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": "4.2", "versionEndExcluding": "5.10.253", "matchCriteriaId": "CC85AD7F-B910-43F1-9A7F-94BC2781DACB"}, {"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/0c7f21d8bd2f93998b72b7a7f93152336aeca4dd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/34a23fd9ddd683a03c7e8cc0ceded3e59e354b99", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/549f02d8ec94d39092ab6d9b103d0d6783a4b024", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9907ac9b9a18b92fc34b9e4cb9e10f208dc1d3f7", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/bfbddeadd4779651403035ee177ae2f22f9f5521", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c97b2a00059608592ad0d86fbb813a4f8cf9464b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d049e56b1739101d1c4d81deedb269c52a8dbba0", "source": "416baaa9-dc ... 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