CVE-2022-49888 is a vulnerability identified in the Linux kernel specifically affecting the arm64 architecture, related to the handling of debug exceptions on Cortex-A76 processors. The issue arises from a regression introduced by a kernel commit that removed the NOKPROBE_SYMBOL() annotation from the function cortex_a76_erratum_1463225_debug_handler(). This function is responsible for handling debug exceptions and synchronous exceptions triggered by BRK instructions. The vulnerability manifests when this function is probed using kprobes, a Linux kernel debugging mechanism. If the function is not inlined by the compiler as intended, it becomes probeable, which leads to recursive debug exceptions when a breakpoint or debug exception occurs. This recursion causes a stack overflow, resulting in a kernel panic and system crash. The vulnerability can be triggered by the ftrace multiple_probes selftest, demonstrating that it is exploitable under certain debugging conditions. The root cause is that cortex_a76_erratum_1463225_debug_handler() was expected to be always inlined into its caller el1_dbg(), which is marked noinstr and cannot be probed, but the removal of the NOKPROBE_SYMBOL() annotation allowed it to be probed directly. The fix involves marking the function as __always_inline to ensure it cannot be probed independently, thus preventing recursive exceptions and stack overflow. This vulnerability affects Linux kernel versions containing the specific commit 6459b8469753e9feaa8b34691d097cffad905931 and impacts systems running on ARM64 Cortex-A76 CPUs. It is a low-level kernel issue tied to debugging infrastructure and CPU erratum workarounds.

For European organizations, the impact of CVE-2022-49888 depends largely on the deployment of Linux systems running on ARM64 Cortex-A76 processors, which are common in certain embedded systems, servers, and cloud infrastructure. The vulnerability can cause kernel panics and system crashes when debug probes are used, potentially leading to denial of service (DoS) conditions. While exploitation requires the ability to insert kprobes on the vulnerable function, which typically requires privileged access, an attacker or misconfigured debugging environment could trigger system instability or outages. This could disrupt critical services, especially in sectors relying on ARM64-based Linux servers or embedded devices such as telecommunications, industrial control systems, or cloud providers using ARM-based infrastructure. The vulnerability does not appear to allow privilege escalation or code execution beyond causing a kernel stack overflow and panic. However, the resulting DoS could impact availability of services and systems, leading to operational disruptions and potential financial or reputational damage. Since the vulnerability is tied to debugging mechanisms, it is less likely to be exploited remotely without prior access, but insider threats or compromised administrators could leverage it. The lack of known exploits in the wild reduces immediate risk, but organizations should remain vigilant.

To mitigate CVE-2022-49888, organizations should ensure that their Linux kernel versions are updated to include the patch that marks cortex_a76_erratum_1463225_debug_handler() as __always_inline, preventing it from being probed and thus avoiding recursive exceptions. Kernel upgrades should be prioritized on ARM64 Cortex-A76 systems, especially those used in production or critical environments. Additionally, restrict and monitor the use of kprobes and other kernel debugging tools to trusted administrators only, as misuse or unauthorized access could trigger the vulnerability. Implement strict access controls and auditing on /sys/kernel/debug/tracing interfaces to prevent unauthorized probe insertion. For environments where kernel upgrades are delayed, consider disabling or limiting kernel debugging features if feasible, to reduce attack surface. Regularly review kernel logs and system behavior for signs of kernel panics or stack overflows that could indicate attempts to exploit this vulnerability. Collaborate with hardware and OS vendors to ensure timely patch deployment and verify that ARM64-based systems are running supported and updated kernel versions. Finally, incorporate this vulnerability into incident response and vulnerability management workflows to ensure rapid detection and remediation.