Bug 2520161 (CVE-2026-18917)

Summary: CVE-2026-18917 libvirt: Integer overflow in NodeGetFreePages RPC handler leading to heap buffer overflow
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in libvirt. An unprivileged local user could exploit an integer overflow vulnerability in the NodeGetFreePages RPC handler. This flaw allows crafted values to bypass a size check, leading to an undersized memory buffer. Subsequently, real NUMA node data can overwrite this buffer. This heap buffer overflow can corrupt the root libvirt daemon's memory, potentially leading to a denial of service or local privilege escalation.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2520165    
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Description OSIDB Bzimport 2026-08-20 09:04:51 UTC 
An integer overflow vulnerability was found in libvirt's NodeGetFreePages RPC handler in src/remote/remote_daemon_dispatch.c. The dispatcher computes a 32-bit product (pages_len * cellCount) for both validation and memory allocation. While pages_len is XDR-capped at 1024, cellCount remains unbounded. The multiplication truncates modulo 2^32, allowing crafted values to bypass the guard check. The undersized buffer is then overwritten with real NUMA node data. The RPC call requires only connect:read ACL (lowest permission tier) and is accessible via the world-readable Unix socket (mode 0666) with no authentication for VIR_CONNECT_RO clients. An unprivileged local user could exploit this to corrupt the root libvirt daemon's heap, leading to denial of service or potentially local privilege escalation.
Comment 1 Mauro Matteo Cascella 2026-08-20 09:10:21 UTC 
Upstream issue & patch:
- https://gitlab.com/libvirt/libvirt/-/work_items/903
- https://gitlab.com/libvirt/libvirt/-/commit/5a62cbf2907d4590283597b46da9c0f41e7b4d4f