CVE-2026-29645
NEMU RISC-V Vector Decoder Improper Instruction Validation
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.
INFO
Published Date :
April 20, 2026, 8:16 p.m.
Last Modified :
April 24, 2026, 7:25 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Update NEMU to version v2025.12.r2 or later.
- Ensure correct instruction validation in the RVV decoder.
- Apply patches for the funct3 field validation.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-29645.
| URL | Resource |
|---|---|
| https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html | Product |
| https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039 | Patch |
| https://github.com/OpenXiangShan/NEMU/issues/952 | Issue Tracking |
| https://github.com/OpenXiangShan/NEMU/pull/958 | Issue Tracking |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-29645 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-29645
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-29645 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-29645 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 24, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:xiangshan:nemu:2025.12:r1:*:*:*:*:*:* Added Reference Type MITRE: https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html Types: Product Added Reference Type MITRE: https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039 Types: Patch Added Reference Type MITRE: https://github.com/OpenXiangShan/NEMU/issues/952 Types: Issue Tracking Added Reference Type MITRE: https://github.com/OpenXiangShan/NEMU/pull/958 Types: Issue Tracking -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 21, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-131 Added CWE CWE-1287 -
New CVE Received by [email protected]
Apr. 20, 2026
Action Type Old Value New Value Added 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. Added Reference https://docs.riscv.org/reference/isa/unpriv/v-st-ext.html Added Reference https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039 Added Reference https://github.com/OpenXiangShan/NEMU/issues/952 Added Reference https://github.com/OpenXiangShan/NEMU/pull/958