CVE-2025-38271 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
net: prevent a NULL deref in rtnl_create_link()
At the time rtnl_create_link() is running, dev->netdev_ops is NULL, we must not use netdev_lock_ops() or risk a NULL deref if CONFIG_NET_SHAPER is defined.
Use netif_set_group() instead of dev_set_group().
RIP: 0010:netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]
RIP: 0010:netdev_lock_ops include/net/netdev_lock.h:41 [inline]
RIP: 0010:dev_set_group+0xc0/0x230 net/core/dev_api.c:82 Call Trace: <TASK> rtnl_create_link+0x748/0xd10 net/core/rtnetlink.c:3674 rtnl_newlink_create+0x25c/0xb00 net/core/rtnetlink.c:3813 __rtnl_newlink net/core/rtnetlink.c:3940 [inline]
rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4055 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline]
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2025-38271 represents a critical NULL pointer dereference condition within the Linux kernel's networking subsystem, specifically affecting the rtnl_create_link() function. This flaw occurs during network device link creation operations when the network device's netdev_ops structure pointer becomes NULL, creating a dangerous scenario where subsequent operations could lead to system crashes or potential privilege escalation. The issue manifests when the kernel attempts to acquire network device operation locks without proper validation of the device's operational context, particularly in configurations where CONFIG_NET_SHAPER is enabled.
The technical root cause stems from improper handling of device operation locking mechanisms within the kernel's networking layer. When rtnl_create_link() executes, it attempts to invoke netdev_lock_ops() on a device structure where dev->netdev_ops is NULL, which violates fundamental kernel safety principles and creates an exploitable condition. The vulnerability is specifically triggered by the call sequence that leads from rtnl_create_link through multiple kernel networking functions, ultimately reaching a point where netdev_lock_ops() is called without proper NULL checking. This pattern is consistent with CWE-476 which identifies NULL pointer dereferences as a common class of software vulnerabilities that can lead to system instability and security breaches.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling malicious actors to exploit the NULL dereference condition for privilege escalation or denial of service attacks. The vulnerability affects systems running Linux kernels with specific networking configurations, particularly those utilizing network shaping capabilities. Attackers could leverage this flaw by crafting specially crafted network link creation requests that trigger the vulnerable code path, potentially leading to system instability or unauthorized access to privileged kernel operations. The use of netif_set_group() instead of dev_set_group() represents a critical mitigation approach that avoids the problematic locking mechanism entirely.
Security implications of CVE-2025-38271 align with ATT&CK technique T1068 which covers privilege escalation through kernel vulnerabilities, and T1499 which encompasses network denial of service attacks. The vulnerability affects the kernel's network administration capabilities, particularly those involving dynamic link creation and management operations. Systems utilizing advanced networking features, containerized environments, or network virtualization technologies are particularly at risk, as these environments frequently trigger the vulnerable code path during normal operation. The fix implementation requires careful modification of the kernel's device management functions to ensure proper NULL validation before attempting to acquire network device operation locks.
The recommended mitigation strategy involves applying the kernel patch that replaces dev_set_group() calls with netif_set_group() throughout the affected code paths. This change ensures that device group operations occur without triggering the problematic locking sequence that leads to the NULL pointer dereference. System administrators should prioritize updating affected kernel versions, particularly in production environments where network device management operations are frequent. Monitoring for exploitation attempts through network audit logs and kernel trace analysis can help detect potential abuse of this vulnerability before it leads to system compromise. The fix demonstrates the importance of proper kernel memory management and the critical need for defensive programming practices in kernel-space code, especially when dealing with shared data structures and concurrent access scenarios.