CVE-2022-50883: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50883 is a vulnerability in the Linux kernel's BPF (Berkeley Packet Filter) subsystem where a decl_tag type can be improperly referenced as a function prototype argument during BTF (BPF Type Format) validation. The flaw was discovered via Syzkaller fuzzing and publicly disclosed on December 30, 2025. It affects Linux kernel versions from the initial commit (1da177e4c3f4) up to the fixes applied in stable releases 5.4.229, 5.10.163, 5.15.86, 6.0.16, 6.1.2, and 6.2. The CVSS category is estimated as Medium, with an EPSS score of 0.024% (Feedly, EUVD).

The root cause is insufficient validation in the BTF type-checking logic within kernel/bpf/btf.c, specifically in btf_func_proto_check(). When parsing BTF type sections via the bpf() syscall (BPF_BTF_LOAD command), the kernel fails to reject BTF_KIND_DECL_TAG types when they appear as function prototype arguments, which is semantically invalid. This is analogous to a previously fixed issue (commit ea68376c8bed) that prevented decl_tag from being referenced as a function prototype return type, but the argument path was left unguarded. The vulnerability is classified under improper input validation (CWE-20) and is reachable locally via the bpf() syscall, requiring CAP_BPF or equivalent privileges on most modern Linux configurations (Feedly).

Exploitation of this vulnerability can cause a kernel crash or undefined behavior due to improper BTF type graph traversal, impacting system availability. Because the flaw is triggered through the bpf() syscall during BTF loading, a local attacker with sufficient privileges could cause a denial of service (kernel panic or instability). There is no evidence of confidentiality or integrity impact beyond system availability disruption (Feedly).

The Linux kernel maintainers have released patches across multiple stable branches. Users should upgrade to the following fixed versions: 5.4.229, 5.10.163, 5.15.86, 6.0.16, 6.1.2, or 6.2 (mainline). The fixes are available via the stable kernel git repository. As a workaround on systems where BPF is not required, restricting access to the bpf() syscall via seccomp filters or setting kernel.unprivileged_bpf_disabled=1 can reduce exposure (Feedly, Kernel Stable).