Host-kernel stack overwrite via oversized vlenb load
Published Sep 16, 2025 · Updated Sep 16, 2025
A stack overwrite in RISC-V KVM in the Linux kernel allows local users with a vCPU descriptor to corrupt host-kernel memory. The kvm_riscv_vcpu_set_reg_vector function passes the size encoded in a KVM_SET_ONE_REG request to copy_from_user for an unsigned-long stack variable without checking that the sizes match. Access to /dev/kvm and a RISC-V host with the V extension is required; crafted sizes and data can panic the host or enable kernel code execution.
Summary
What happened
A stack overwrite in RISC-V KVM in the Linux kernel allows local users with a vCPU descriptor to corrupt host-kernel memory. The kvm_riscv_vcpu_set_reg_vector function passes the size encoded in a KVM_SET_ONE_REG request to copy_from_user for an unsigned-long stack variable without checking that the sizes match. Access to /dev/kvm and a RISC-V host with the V extension is required; crafted sizes and data can panic the host or enable kernel code execution.
The record
- CVE
- CVE-2025-39815
- Published
- Sep 16, 2025
- Updated
- Sep 16, 2025
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1068
- Attack vector
- local
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 16, 2025CVE publishedPublication date reported by the CVE source.
- Sep 16, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2fa290372dfe7dd248b1c16f943f273a3e674f22 <6d28659b692a0212f360f8bd8a58712b339f9aac
- Affected versionversion=2fa290372dfe7dd248b1c16f943f273a3e674f22 <799766208f09f95677a9ab111b93872d414fbad7
- Affected versionversion=2fa290372dfe7dd248b1c16f943f273a3e674f22 <c76bf8359188a11f8fd790e5bbd6077894a245cc
- Affected versionversion=6.8
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
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
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo