QEMU uefi-vars Buffer Size vs Transfer I/O Info Leak
CVE-2025-8860 Published on February 18, 2026
Qemu-kvm: uefi-vars: information disclosure vulnerability in uefi_vars_write callback
A flaw was found in QEMU in the uefi-vars virtual device. When the guest writes to register UEFI_VARS_REG_BUFFER_SIZE, the .write callback `uefi_vars_write` is invoked. The function allocates a heap buffer without zeroing the memory, leaving the buffer filled with residual data from prior allocations. When the guest later reads from register UEFI_VARS_REG_PIO_BUFFER_TRANSFER, the .read callback `uefi_vars_read` returns leftover metadata or other sensitive process memory from the previously allocated buffer, leading to an information disclosure vulnerability.
Vulnerability Analysis
CVE-2025-8860 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
Improper Removal of Sensitive Information Before Storage or Transfer
The product stores, transfers, or shares a resource that contains sensitive information, but it does not properly remove that information before the product makes the resource available to unauthorized actors.
Products Associated with CVE-2025-8860
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Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.