CVE-2026-29649

Service interruption via coupled hypervisor CSR fields

Published Apr 20, 2026 · Updated Apr 20, 2026

Protection mechanism failure in NEMU's RISC-V hypervisor CSR handling allows context-dependent attackers to interrupt emulation in V=1 contexts. The CSR read logic masks henvcfg[7:4] through menvcfg[7:4], incorrectly coupling the CBIE, CBCFE, and CBZE fields so menvcfg changes alter the visible hypervisor configuration. The condition requires virtualized V=1 execution after the relevant machine-mode configuration changes; cache-block management instructions can then raise unexpected traps and deny availability.

CVSS severity9.8
Critical
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Protection mechanism failure in NEMU's RISC-V hypervisor CSR handling allows context-dependent attackers to interrupt emulation in V=1 contexts. The CSR read logic masks henvcfg[7:4] through menvcfg[7:4], incorrectly coupling the CBIE, CBCFE, and CBZE fields so menvcfg changes alter the visible hypervisor configuration. The condition requires virtualized V=1 execution after the relevant machine-mode configuration changes; cache-block management instructions can then raise unexpected traps and deny availability.

The record

CVE
CVE-2026-29649
Published
Apr 20, 2026
Updated
Apr 20, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-693, T1499.004
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Apr 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-693Protection Mechanism Failure
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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