CVE-2023-53857: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53857 is a Linux kernel vulnerability in the BPF (Berkeley Packet Filter) subsystem, specifically in the bpf_sk_storage component, caused by an invalid wait context that triggers a lockdep splat. The flaw was published on December 9, 2025, and affects the Linux kernel in versions where bpf_local_storage_update can be called while holding an RCU read lock and a storage lock, leading to an improper attempt to acquire a local_lock with an incompatible lock context. Feedly estimates the severity as Medium, with an EPSS score of 0.000180, indicating very low likelihood of exploitation in the wild (Feedly).

The root cause is an invalid locking context (CWE-667: Improper Locking) within the bpf_sk_storage path of the Linux kernel's BPF local storage subsystem. When bpf_local_storage_update() is invoked while holding an RCU read lock (rcu_read_lock, context {1:3}) and a storage spinlock (&storage->lock, context {2:2}), it subsequently attempts to acquire a local_lock (stock_lock, context {3:3}) — a per-CPU lock that requires a process context ({5:5}). This mismatch is detected by the kernel's lockdep validator and results in a warning/splat, as reported by running ./test_progs -t test_local_storage on kernel 6.5.0. The fix is tracked in upstream kernel commits 300415caa373 and a96a44aba556 (Feedly).

The primary impact of this vulnerability is a kernel lockdep warning (splat) that can indicate a potential deadlock condition or kernel instability in systems using BPF local socket storage. In practice, the invalid wait context could lead to system hangs or kernel panics under specific workloads that exercise the affected BPF storage path, affecting availability. There is no evidence of confidentiality or integrity impact, and the vulnerability does not appear to be directly exploitable for privilege escalation or data exfiltration (Feedly).

The fix has been applied to the Linux kernel via upstream commits 300415caa373a07782fcbc2f8d9429bc2dc27a47 and a96a44aba556c42b432929d37d60158aca21ad4c. Users should update to a patched kernel version that includes these commits. SUSE has issued advisories (SUSE-2026-0281-1 and SUSE-2026-20876-1) incorporating the fix for their kernel packages. As a workaround, systems not relying on BPF local socket storage functionality can disable or avoid loading the affected BPF programs, though upgrading the kernel is the recommended remediation (Feedly, Linux Security).