Ampere AmpereOne CVE-2025-62863

Exploitation requires the ability to issue a (malformed) SMC call to the UEFI-MM PCIe driver - an operation only available to code executing at the normal-world OS kernel/hypervisor privilege level (EL1+) on AArch64, since SMC is a privileged instruction. The attacker must therefore already hold kernel-level control on an affected AmpereOne AC03/AC04/M server running firmware below the fixed versions; this is not reachable by an unauthenticated remote user despite the input's AV:N rating. The limiting factors are the mandatory pre-existing privileged execution context and the requirement to run on specific unpatched AmpereOne firmware revisions.

The input assigns CVSS 9.8 with vector AV:N/AC:L/PR:N/UI:N, which treats this as a remote, unauthenticated, network-reachable flaw - but that rating conflicts directly with the technical description. The vulnerability is triggered by an 'incorrectly formed SMC call' to the UEFI-MM (Management Mode) PCIe driver, and SMC (Secure Monitor Call) instructions can only be issued by code already running at the OS kernel level (EL1) or higher on the ARM AArch64 platform. This means a network-only, zero-privilege attacker almost certainly CANNOT reach this code path directly; realistic exploitation presupposes prior privileged (kernel/hypervisor-level) code execution in the normal world. Therefore the AV:N/PR:N portion of the input CVSS appears materially overstated - verify with Ampere advisory AMP-SB-0007. On other signals: there is no CISA KEV listing and no public exploit identified, so there is no evidence of active exploitation or weaponization. The genuine concern is high technical impact (out-of-bounds write in secure S-EL0 address space, enabling a trust-boundary crossing from the normal world into secure firmware), not ease of initial access. Net assessment: this is a high-severity firmware/secure-world privilege-escalation primitive rather than the internet-facing, trivially-exploitable 9.8 the headline score implies; priority is real for affected Ampere server fleets but should be weighted by the local-privilege prerequisite.

An attacker who has already achieved kernel-level code execution on an AmpereOne server (for example via a prior OS/hypervisor compromise or a malicious privileged tenant) issues a malformed SMC call to the UEFI-MM PCIe driver, triggering an out-of-bounds write inside the driver's secure S-EL0 address space. By controlling the corrupted secure-world memory, the attacker escalates from normal-world privilege into the firmware trust domain, undermining platform/secure-boot integrity. No public proof-of-concept is currently identified, and the SMC-based trigger implies low complexity once the required privilege level is held.