Cybersecurity researchers have unveiled what they claim to be the “first native Spectre v2 exploit” against the Linux kernel on Intel systems, potentially enabling the leakage of sensitive data from memory.
The exploit, dubbed Native Branch History Injection (BHI), can be used to extract arbitrary kernel memory at a rate of 3.5 kB/sec by circumventing existing Spectre v2/BHI mitigations, according to researchers from the Systems and Network Security Group (VUSec) at Vrije Universiteit Amsterdam.
The vulnerability tracked as CVE-2024-2201, was first disclosed by VUSec in March 2022, describing a technique that can bypass Spectre v2 protections in modern processors from Intel, AMD, and Arm.
While the attack leveraged extended Berkeley Packet Filters (eBPFs), Intel’s recommendations to address the issue included disabling Linux’s unprivileged eBPFs. However, the new Native BHI exploit neutralizes this countermeasure by demonstrating that BHI is possible without eBPF, affecting all Intel systems susceptible to the vulnerability.
The CERT Coordination Center (CERT/CC) warned that existing mitigation techniques, such as disabling privileged eBPF and enabling (Fine)IBT, are insufficient in stopping BHI exploitation against the kernel/hypervisor. “An unauthenticated attacker can exploit this vulnerability to leak privileged memory from the CPU by speculatively jumping to a chosen gadget,” the advisory stated.
The disclosure comes weeks after researchers detailed GhostRace (CVE-2024-2193), a variant of Spectre v1 that combines speculative execution and race conditions to leak data from contemporary CPU architectures. It also follows new research from ETH Zurich that unveiled a family of attacks, dubbed Ahoi Attacks, that could compromise hardware-based trusted execution environments (TEEs) and break confidential virtual machines (CVMs) like AMD Secure Encrypted Virtualization-Secure Nested Paging (SEV-SNP) and Intel Trust Domain Extensions (TDX).
In response to the Ahoi Attacks findings, AMD acknowledged the vulnerability is rooted in the Linux kernel implementation of SEV-SNP and stated that fixes addressing some of the issues have been upstreamed to the main Linux kernel.
