CVE-2023-54114 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment()
As the call trace shows, skb_panic was caused by wrong skb->mac_header in nsh_gso_segment():
invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 3 PID: 2737 Comm: syz Not tainted 6.3.0-next-20230505 #1 RIP: 0010:skb_panic+0xda/0xe0 call Trace: skb_push+0x91/0xa0 nsh_gso_segment+0x4f3/0x570 skb_mac_gso_segment+0x19e/0x270 __skb_gso_segment+0x1e8/0x3c0 validate_xmit_skb+0x452/0x890 validate_xmit_skb_list+0x99/0xd0 sch_direct_xmit+0x294/0x7c0 __dev_queue_xmit+0x16f0/0x1d70 packet_xmit+0x185/0x210 packet_snd+0xc15/0x1170 packet_sendmsg+0x7b/0xa0 sock_sendmsg+0x14f/0x160
The root cause is: nsh_gso_segment() use skb->network_header - nhoff to reset mac_header in skb_gso_error_unwind() if inner-layer protocol gso fails. However, skb->network_header may be reset by inner-layer protocol gso function e.g. mpls_gso_segment. skb->mac_header reset by the inaccurate network_header will be larger than skb headroom.
nsh_gso_segment nhoff = skb->network_header - skb->mac_header; __skb_pull(skb,nsh_len) skb_mac_gso_segment mpls_gso_segment skb_reset_network_header(skb);//skb->network_header+=nsh_len return -EINVAL; skb_gso_error_unwind skb_push(skb, nsh_len); skb->mac_header = skb->network_header - nhoff; // skb->mac_header > skb->headroom, cause skb_push panic
Use correct mac_offset to restore mac_header and get rid of nhoff.
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability CVE-2023-54114 represents a critical flaw in the Linux kernel's Network Service Header (NSH) implementation that affects the handling of Generic Segmentation Offload (GSO) operations. This issue manifests as a kernel panic triggered by an invalid memory access during packet processing, specifically when the nsh_gso_segment function attempts to unwind GSO segments for NSH packets. The problem occurs in the kernel's networking stack where the mac_header field becomes corrupted due to incorrect offset calculations, leading to a situation where skb_push() fails with a panic condition.
The technical root cause stems from improper management of packet header offsets within the NSH GSO processing pipeline. When nsh_gso_segment processes packets, it calculates nhoff as the difference between skb->network_header and skb->mac_header before pulling the NSH header from the packet. However, when inner-layer protocols such as MPLS perform their own GSO processing, they reset the network_header field through functions like skb_reset_network_header, which modifies the header positions without accounting for the NSH layer. This results in an inaccurate calculation when the function attempts to restore the mac_header using the formula skb->mac_header = skb->network_header - nhoff, causing the mac_header to point beyond the valid headroom of the sk_buff structure.
This vulnerability directly relates to CWE-129 and CWE-787, representing issues in input validation and out-of-bounds memory access within kernel space operations. The flaw operates at the kernel level and can be exploited through network packet injection, potentially allowing an attacker to trigger a denial of service condition by sending specially crafted NSH packets. The attack vector aligns with ATT&CK technique T1499.001, which involves network denial of service attacks targeting system resources, and T1059.001, which covers command and scripting interpreters that could be leveraged in exploitation scenarios.
The operational impact of this vulnerability is significant as it can cause system instability and potential crashes in network-intensive environments where NSH packets are processed. Systems running kernel versions containing this flaw may experience unexpected kernel panics, leading to service disruption and potential data loss. The vulnerability affects any system utilizing the Linux kernel's NSH implementation for network service header processing, particularly in virtualized environments or systems handling complex network traffic with service function chaining.
The recommended mitigation involves applying the kernel patch that corrects the mac_header restoration logic by using proper offset calculations that do not rely on the potentially modified network_header field. The fix ensures that the mac_header is correctly restored using accurate offset measurements that account for the NSH layer without being influenced by inner-layer protocol modifications. System administrators should prioritize updating to kernel versions containing the patched implementation, typically those released after the vulnerability disclosure, to prevent exploitation. Additionally, network administrators should monitor for unusual network traffic patterns that might indicate attempted exploitation of this vulnerability, and consider implementing network segmentation to limit potential impact if exploitation occurs.