Bug 2536972

Summary: CVE-2026-81627 unicorn: VAPIC writable ROM alias can escape the option-ROM window and expose locked SMRAM [fedora-all]
Product: [Fedora] Fedora Reporter: Mauro Matteo Cascella <mcascell>
Component: unicornAssignee: W. Michael Petullo <redhat>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: epel-packagers-sig, redhat
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["ef621f7d-ef08-4087-8b3a-a7bca7c90b7d"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 2536950    

Description Mauro Matteo Cascella 2026-09-18 10:41:26 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

A flaw was found in QEMU's VAPIC (Virtual Advanced Programmable Interrupt Controller) implementation in hw/i386/vapic.c. The 16-bit VAPIC setup hypercall allows a privileged guest to specify both the base address and size of a high-priority writable RAM alias. QEMU does not validate that this alias remains within the VAPIC option ROM boundaries (0xc0000..0xdffff). A malicious guest administrator can place the alias over 0xa0000..0xbffff, bypassing the Q35 chipset's D_LCK-protected SMRAM and modifying memory that executes in System Management Mode. This could allow a privileged guest user to inject arbitrary code into locked SMRAM.

Upstream fix: https://gitlab.com/qemu-project/qemu/-/commit/d61c8a6fb7388486353aa267ba0d75b098f16662

Reference: https://gitlab.com/qemu-project/qemu/-/work_items/4206