CVE-2024-43817 in Linux
Sumário
de VulDB • 10/05/2026
No, this is not a kernel bug.
The crash occurs in `ip_do_fragment` during IP packet fragmentation, triggered by a `sendto()` syscall via a packet socket (`af_packet`). The call trace shows the packet is being transmitted through an `ipip6` tunnel (`sit_tunnel_xmit`), which is a legacy IPv6-to-IPv4 tunneling mechanism.
The key indicator is the `CR2` register value: `000000002000f000`. This is a user-space address (typically in the range `0x0000...` to `0x7fff...` on 64-bit systems, but here it's `0x2000f000`, which is a valid user-space virtual address). Kernel NULL pointer dereferences or invalid kernel address dereferences would show a `CR2` value of `0x0000000000000000` or a high kernel-space address (e.g., `0xffff...`).
This strongly suggests that the kernel is dereferencing a pointer that was copied from user space, but the user-space buffer was unmapped, freed, or corrupted before the kernel could safely access it. This is a classic race condition or use-after-free in the **user-space application** that is sending the packet, not a bug in the kernel itself.
The kernel correctly handles the packet until it needs to fragment it. During fragmentation, it may need to access the original packet data or headers. If the user-space application has already freed or unmapped the buffer associated with the `sendto()` call, the kernel's attempt to access that memory results in a page fault on a user-space address, leading to the crash.
**Conclusion:** The bug is in the user-space application that is sending the packet via the packet socket. The application is likely freeing or unmapping the buffer before the kernel has finished processing the packet, especially during the fragmentation path. The kernel is not at fault; it is correctly crashing because it is accessing invalid user-space memory.
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