CVE-2026-29645

Description

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0003

Probability of exploitation

0.09%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-131 CWE-131

CWE-1287 CWE-1287

Affected Products

Vendor	Product	Versions
xiangshan	nemu	All

References

Advisories & Patches

https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039

Other References

https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html https://github.com/OpenXiangShan/NEMU/issues/952 https://github.com/OpenXiangShan/NEMU/pull/958

Frequently Asked Questions

What is CVE-2026-29645? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-29645? +

CVE-2026-29645 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0003, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-29645? +

CVE-2026-29645 affects products from xiangshan, specifically: nemu. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-29645? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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