CVE-2026-29646

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{"affected": [{"affectedData": [{"product": "n/a", "vendor": "n/a", "versions": [{"status": "affected", "version": "n/a"}]}], "source": "cve@mitre.org"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In OpenXiangShan NEMU prior to 55295c4, when running with RVH (Hypervisor extension) enabled, a VS-mode guest write to the supervisor interrupt-enable CSR (sie) may be handled incorrectly and can influence machine-level interrupt enable state (mie). This breaks privilege/virtualization isolation and can lead to denial of service or privilege-boundary violation in environments relying on NEMU for correct interrupt virtualization."}, {"lang": "es", "value": "En OpenXiangShan NEMU anterior a 55295c4, cuando se ejecuta con RVH (extensi\u00f3n de hipervisor) habilitado, una escritura de invitado en modo VS en el CSR de habilitaci\u00f3n de interrupciones del supervisor (sie) puede manejarse incorrectamente y puede influir en el estado de habilitaci\u00f3n de interrupciones a nivel de m\u00e1quina (mie). Esto rompe el aislamiento de privilegios/virtualizaci\u00f3n y puede conducir a la denegaci\u00f3n de servicio o a una violaci\u00f3n del l\u00edmite de privilegios en entornos que dependen de NEMU para una virtualizaci\u00f3n de interrupciones correcta."}], "id": "CVE-2026-29646", "lastModified": "2026-11-11T19:10:00.360", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-29646", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-04-21T13:53:04.119813Z", "version": "2.0.3"}}]}, "published": "2026-04-20T21:16:19.503", "references": [{"source": "cve@mitre.org", "url": "https://docs.riscv.org/reference/isa/priv/hypervisor.html"}, {"source": "cve@mitre.org", "url": "https://docs.riscv.org/reference/isa/priv/machine.html"}, {"source": "cve@mitre.org", "url": "https://docs.riscv.org/reference/isa/priv/supervisor.html"}, {"source": "cve@mitre.org", "url": "https://docs.riscv.org/reference/isa/unpriv/zicsr.html"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/issues/951"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/pull/938"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/pull/938/commits/55295c46580456d8d5a9d5736e1fda924b8825ab"}], "sourceIdentifier": "cve@mitre.org", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-267"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[0,55295c4)"}}], "enrichment": {"confidence": 80.0, "confidence_source": "inferred", "scores": [{"score": 80.0, "source": "inferred"}]}, "original": {"product": "n/a", "source": "cna", "vendor": "n/a"}, "product": "nemu", "vendor": "openxiangshan"}], "analysis": {"en": {"generated_at": "2026-04-22T08:07:13.764839+00:00", "value": {"mitigation_remediation": ["Upgrade OpenXiangShan NEMU to a build containing commit\u00a055295c4 or later.", "Disable the hypervisor extension (RVH) or run the emulator without hypervisor mode to exclude the vulnerable path.", "Until an official upgrade is available, isolate the NEMU environment from critical workloads and monitor for unexpected changes to machine\u2011level interrupt registers."], "summary": {"action": "Apply Patch", "impact": "Privilege Escalation and Denial of Service"}, "threat_synthesis": {"affected_systems": "All OpenXiangShan NEMU builds executed before commit 55295c4 and run with RVH enabled are vulnerable. The issue exists on any installation that has not incorporated the patch from pull request 938. No other vendor or product variants are identified.", "description_and_impact": "The vulnerability in OpenXiangShan NEMU occurs when a guest operating system running in VS\u2011mode writes to the supervisor interrupt\u2011enable CSR (sie) while the hypervisor extension (RVH) is enabled. The write is handled incorrectly and can modify the machine\u2011level interrupt enable register (mie), breaking the isolation between privilege layers. An attacker who can control a guest can therefore influence host interrupt handling, potentially leading to a denial of service or to a breach of the privileged boundary. The flaw is an improper enforcement of privilege boundaries (CWE\u2011267).", "risk_and_exploitability": "The CVSS score of 9.8 indicates a high severity threat. The EPSS score of less than 1% and the absence from the CISA KEV catalog suggest that public exploitation is unlikely at present, but the vulnerability, associated with CWE\u2011267, remains actionable in environments that rely on NEMU for isolation. Exploitation requires local control of a VS\u2011mode guest, so the attack surface is limited to systems that host NEMU. Because the impact can cause a denial of service or privilege escalation, the overall risk is moderate to high for those systems."}}}}, "created": "2026-04-21T00:15:16.115512+00:00", "title": "Privilege and Virtualization Isolation Breach in OpenXiangShan NEMU", "updated": "2026-04-28T09:26:45.623312+00:00", "vendors": ["openxiangshan", "openxiangshan$PRODUCT$nemu"]}