CVE-2026-17503 in PowerVM Hypervisor
Summary
by MITRE • 09/24/2026
IBM PowerVM Hypervisor FW1120.00 through FW1120.01, FW1110.00 through FW1110.31, FW1060.00 through FW1060.81, and FW950.00 through FW950.H3 is affected by a vulnerability in the partition firmware runtime boot configuration. An attacker with root access to a partition can maliciously alter partition nvram, causing the partition to fail to boot. This condition persists until operator intervention — deleting and recreating the partition configuration — to restore normal operation. Successful exploitation results in an integrity and availability impact.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified within IBM PowerVM Hypervisor firmware versions FW1120.00 through FW1120.01, FW1110.00 through FW1110.31, FW1060.00 through FW1060.81, and FW950.00 through FW950.H3 represents a critical flaw in the partition firmware runtime boot configuration mechanism. This issue specifically targets the Non-Volatile Random Access Memory (NVRAM) structures that store essential boot parameters for logical partitions managed by the PowerVM hypervisor. The core technical deficiency lies in the insufficient validation and integrity checking of NVRAM modifications performed during the runtime environment, allowing a compromised entity with elevated privileges to corrupt these critical configuration blocks without triggering immediate system-level safeguards or rollback mechanisms.
An attacker who has achieved root access within an affected partition is positioned to exploit this weakness by directly manipulating the partition's NVRAM contents. By maliciously altering specific boot configuration variables stored in non-volatile memory, the attacker can render the partition unable to initialize its operating system upon subsequent restarts. This manipulation does not require physical access or external network intrusion once root privileges are established within a single virtual machine, highlighting a severe breakdown in isolation boundaries and privilege separation expectations between guest partitions and the underlying hypervisor management plane for configuration persistence.
The operational impact of this vulnerability is characterized by a significant degradation of availability and data integrity. When the NVRAM boot configuration is corrupted, the partition enters a failed state where it cannot proceed past the initial boot sequence. This condition persists indefinitely until manual intervention occurs at the hardware or hypervisor management level. Restoring normal operation requires an operator to delete the compromised partition configuration entirely and recreate it from scratch, effectively resulting in data loss if persistent storage within that partition was not backed up externally. This process disrupts service continuity and imposes a heavy administrative burden for recovery, particularly in environments with numerous virtual machines or automated orchestration systems that rely on stable boot states.
From a classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write if the corruption involves memory structure overruns during NVRAM simulation, but more accurately maps to CWE-354: Improper Validation of Integrity Check Value due to the failure to verify that modifications to boot configuration are legitimate and untampered. In terms of adversary behavior as defined by MITRE ATT&CK, this exploitation technique corresponds to T1078: Valid Accounts combined with T1229: System Firmware or T1564: Hidden Files and Directories if the attacker attempts to obscure the modification, though primarily it reflects a privilege escalation leading to denial of service via configuration corruption. The attack vector is classified as local with high privileges required, indicating that while not remotely exploitable by default, it poses severe risk in multi-tenant environments where lateral movement or initial compromise of any partition can lead to widespread outages through cascading failures if other partitions depend on shared resources or management interfaces.
Mitigation strategies must focus on strict access control and monitoring rather than relying solely on software patches for the firmware versions listed, as the flaw is inherent in the design of how NVRAM changes are processed at runtime. Organizations should enforce least-privilege principles to ensure that no single partition obtains root-level access without rigorous auditing and justification. Implementing robust backup procedures for partition configurations before any maintenance or high-risk operations can reduce recovery time significantly. Additionally, enabling detailed audit logging on the hypervisor level to detect unauthorized attempts to modify NVRAM structures can provide early warning indicators of such exploitation activities. Regular updates to newer firmware versions that address this specific validation logic are essential when available from IBM to close the gap in integrity verification for partition boot parameters.