{"dataType": "CVE_RECORD", "cveMetadata": {"state": "PUBLISHED", "cveId": "CVE-2026-29645", "assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca", "assignerShortName": "mitre", "dateUpdated": "2026-04-20T19:24:42.410Z", "dateReserved": "2026-03-04T00:00:00.000Z", "datePublished": "2026-04-20T00:00:00.000Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca", "shortName": "mitre", "dateUpdated": "2026-04-20T19:24:42.410Z"}, "descriptions": [{"lang": "en", "value": "NEMU (OpenXiangShan/NEMU) before v2025.12.r2 contains an improper instruction-validation flaw in its RISC-V Vector (RVV) decoder. The decoder does not correctly validate the funct3 field when decoding vsetvli/vsetivli/vsetvl, allowing certain invalid OP-V instruction encodings to be misinterpreted and executed as vset* configuration instructions rather than raising an illegal-instruction exception. This can be exploited by providing crafted RISC-V binaries to cause incorrect trap behavior, architectural state corruption/divergence, and potential denial of service in systems that rely on NEMU for correct execution or sandboxing."}], "affected": [{"vendor": "n/a", "product": "n/a", "versions": [{"version": "n/a", "status": "affected"}]}], "references": [{"url": "https://github.com/OpenXiangShan/NEMU/issues/952"}, {"url": "https://github.com/OpenXiangShan/NEMU/pull/958"}, {"url": "https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039"}, {"url": "https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html"}], "problemTypes": [{"descriptions": [{"type": "text", "lang": "en", "description": "n/a"}]}]}}, "dataVersion": "5.2"}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "NEMU (OpenXiangShan/NEMU) before v2025.12.r2 contains an improper instruction-validation flaw in its RISC-V Vector (RVV) decoder. The decoder does not correctly validate the funct3 field when decoding vsetvli/vsetivli/vsetvl, allowing certain invalid OP-V instruction encodings to be misinterpreted and executed as vset* configuration instructions rather than raising an illegal-instruction exception. This can be exploited by providing crafted RISC-V binaries to cause incorrect trap behavior, architectural state corruption/divergence, and potential denial of service in systems that rely on NEMU for correct execution or sandboxing."}], "id": "CVE-2026-29645", "lastModified": "2026-04-20T20:16:48.303", "metrics": {}, "published": "2026-04-20T20:16:48.303", "references": [{"source": "cve@mitre.org", "url": "https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/issues/952"}, {"source": "cve@mitre.org", "url": "https://github.com/OpenXiangShan/NEMU/pull/958"}], "sourceIdentifier": "cve@mitre.org", "vulnStatus": "Received"}

{}

{"analysis": {"en": {"generated_at": "2026-04-20T20:43:17.816112+00:00", "value": {"mitigation_remediation": ["Upgrade to NEMU v2025.12.r2 or any later release where the RVV decoder bug is fixed.", "If an immediate upgrade is not possible, isolate NEMU from untrusted binaries, and pre\u2011validate or sanitize input to ensure only legal RVV encodings reach the decoder.", "Monitor emulator log output for abnormal state changes or crashes, and consider disabling the vector extension in NEMU configuration if vector instructions are not required."], "summary": {"action": "Patch", "impact": "Denial of Service and state corruption"}, "threat_synthesis": {"affected_systems": "The vulnerability affects NEMU (OpenXiangShan/NEMU) versions older than v2025.12.r2. No vendor identification beyond the NEMU project is available, and the flaw applies to all installations of the affected emulator that use the RVV decoder.", "description_and_impact": "NEMU (OpenXiangShan/NEMU) before release v2025.12.r2 contains an improper instruction\u2011validation flaw in its RISC\u2011V Vector (RVV) decoder. The decoder fails to validate the funct3 field when decoding the vsetvli/vsetivli/vsetvl instructions, allowing certain malformed OP\u2011V instruction encodings to be interpreted as vset* configuration instructions instead of raising an illegal\u2011instruction exception. This misinterpretation permits the execution of unintended vector setting code, which can corrupt architectural state, trigger incorrect trap handling and lead to a crash or denial of service.", "risk_and_exploitability": "The CVSS score is not provided, and EPSS data is unavailable; the vulnerability is not listed in CISA KEV. Nevertheless, the flaw allows a maliciously crafted RISC\u2011V binary to be supplied to NEMU, which can then be executed and cause state corruption or a denial of service. The attack vector is likely local exploitation via controlled input to NEMU, but systems that expose NEMU as a service could be vulnerable to remote abuse. Given the potential for complete loss of emulator reliability, the risk is considered high, and prompt remediation is advised."}}}}, "created": "2026-04-20T20:45:16.925637+00:00", "title": "Instruction Validation Flaw in NEMU's RISC-V Vector Decoder Allows Misinterpretation of Invalid Encodings", "updated": "2026-04-20T20:45:16.925649+00:00", "vendors": [], "weaknesses": ["CWE-20"]}