CVE-2023-54155: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54155 is a logic flaw in the Linux kernel's XDP (eXpress Data Path) networking subsystem, specifically within the bpf_xdp_adjust_tail() function in net/core/filter.c. The vulnerability stems from an unnecessary frame_sz > PAGE_SIZE check that can trigger unexpected kernel warnings and potentially lead to denial of service or other impacts when processing crafted XDP packets. It affects the Linux kernel and was publicly disclosed on December 24, 2025, via the upstream kernel CVE announcement mailing list. The CVSS v3.1 base score is 7.0 (High), reflecting a local, high-complexity attack requiring low privileges (Red Hat Advisory, Red Hat Bugzilla).

The root cause is a logic flaw (CWE-682: Incorrect Calculation) in bpf_xdp_adjust_tail() where a legacy sanity check — xdp->frame_sz > PAGE_SIZE — was retained after it became obsolete. This check was originally introduced in commit c8741e2bfe87 to catch XDP drivers that had not yet adopted xdp.frame_sz, but became unnecessary once xdp_init_buff() was universally adopted by all XDP drivers. Syzkaller fuzzing discovered that the TUN driver's tun_get_user() path (via tun_build_skb() and tun_alloc_skb()) can produce frame_sz values exceeding PAGE_SIZE (e.g., 131072 bytes) when using contiguous physical memory allocations for higher-order pages, triggering the now-spurious WARN_ON at net/core/filter.c:4121. The fix removes the obsolete check, as XDP is valid on higher-order contiguous physical memory pages (Red Hat Bugzilla).

Successful exploitation by a low-privileged local attacker could cause system instability through kernel warnings and potential denial of service conditions in the network core. The CVSS scoring indicates high confidentiality, integrity, and availability impacts, suggesting that in a worst-case scenario an attacker could potentially escalate privileges or corrupt kernel state, though the primary observed behavior is a kernel WARN_ON triggered via the TUN device interface. The vulnerability's local-only attack vector limits its scope to systems where unprivileged users have access to BPF/XDP functionality and TUN devices (Red Hat Advisory, Red Hat Bugzilla).

The primary remediation is to update the Linux kernel to a patched version that removes the unnecessary frame_sz > PAGE_SIZE check from bpf_xdp_adjust_tail(). Upstream patches are available via the stable kernel tree (commits 20acffcdc2b7, a09c258cfa77, d14eea09edf4, d9252d67ed2f). As interim mitigations, administrators should restrict local user access to BPF/XDP functionality and TUN devices, and consider temporarily disabling XDP if not operationally required. Red Hat has tracked this issue in their security advisory process (Red Hat Advisory, Red Hat Bugzilla).