CVE-2024-26951 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
wireguard: netlink: check for dangling peer via is_dead instead of empty list
If all peers are removed via wg_peer_remove_all(), rather than setting peer_list to empty, the peer is added to a temporary list with a head on the stack of wg_peer_remove_all(). If a netlink dump is resumed and the cursored peer is one that has been removed via wg_peer_remove_all(), it will iterate from that peer and then attempt to dump freed peers.
Fix this by instead checking peer->is_dead, which was explictly created for this purpose. Also move up the device_update_lock lockdep assertion, since reading is_dead relies on that.
It can be reproduced by a small script like:
echo "Setting config..." ip link add dev wg0 type wireguard wg setconf wg0 /big-config ( while true; do echo "Showing config..." wg showconf wg0 > /dev/null done ) & sleep 4 wg setconf wg0 <(printf "[Peer]\nPublicKey=$(wg genkey)\n")
Resulting in:
BUG: KASAN: slab-use-after-free in __lock_acquire+0x182a/0x1b20 Read of size 8 at addr ffff88811956ec70 by task wg/59 CPU: 2 PID: 59 Comm: wg Not tainted 6.8.0-rc2-debug+ #5 Call Trace: <TASK> dump_stack_lvl+0x47/0x70 print_address_description.constprop.0+0x2c/0x380 print_report+0xab/0x250 kasan_report+0xba/0xf0 __lock_acquire+0x182a/0x1b20 lock_acquire+0x191/0x4b0 down_read+0x80/0x440 get_peer+0x140/0xcb0 wg_get_device_dump+0x471/0x1130
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Analysis
by VulDB Data Team • 01/26/2026
The vulnerability described in CVE-2024-26951 affects the Linux kernel's WireGuard implementation, specifically within the netlink interface handling for peer management. This issue arises from an improper check during peer list traversal when peers are removed via the wg_peer_remove_all() function. The flaw stems from a design oversight where the system relies on list emptiness checks rather than explicit peer state indicators, creating a race condition that can lead to use-after-free errors. The vulnerability is categorized under CWE-415 as an improper check for dangling pointers, which is a critical security concern in kernel space operations.
The technical root cause occurs when a WireGuard device undergoes peer removal operations through wg_peer_remove_all(), which moves peers to a temporary stack-based list instead of completely clearing the peer_list. During subsequent netlink dump operations, if the cursor points to a peer that has been moved to this temporary list, the system attempts to traverse and dump freed memory locations. This mismanagement of peer state leads to kernel memory corruption and potential privilege escalation. The fix implemented checks peer->is_dead flag which was specifically designed for this scenario, ensuring proper state validation before peer traversal. This approach aligns with ATT&CK technique T1068 by addressing privilege escalation paths through kernel memory corruption.
The operational impact of this vulnerability is severe as it can be triggered through standard WireGuard configuration operations using the wg command-line tool. The reproduction scenario demonstrates how concurrent configuration updates and netlink dump operations can lead to kernel crashes and memory corruption. The KASAN (Kernel Address Sanitizer) report shows a slab-use-after-free error occurring during lock acquisition, indicating that the system attempts to access freed memory structures. This vulnerability affects systems running Linux kernel versions where WireGuard is enabled and actively used for network configuration, making it particularly dangerous in environments where network security is critical. The fix addresses the issue by ensuring proper locking order and state validation, moving the device_update_lock assertion to occur before reading the is_dead flag, which prevents race conditions during peer state checks.
This vulnerability highlights the importance of proper memory management in kernel space and demonstrates how seemingly minor design decisions can lead to critical security flaws. The solution represents a defensive programming approach that prevents access to freed memory structures by using explicit state flags rather than relying on list emptiness checks. The mitigation strategy requires updating to a patched kernel version that implements the corrected peer state management logic. Organizations should prioritize kernel updates and monitor for similar patterns in other kernel subsystems where peer or object lifecycle management might be similarly flawed. The vulnerability underscores the necessity of thorough testing under concurrent access conditions and proper lock ordering in kernel modules, particularly those handling network configuration and security-related operations.