# CVE-2025-39704: LoongArch: KVM: Fix stack protector issue in send_ipi_data()

> A buffer overflow in the LoongArch KVM module causes a kernel panic when stack protector is enabled, leading to denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Sep 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39704, DEBIAN-CVE-2025-39704, GHSA-g766-4vg6-3q5q, UBUNTU-CVE-2025-39704

## What is CVE-2025-39704?

CVE-2025-39704 is a high-severity memory corruption vulnerability in Linux kernel, published on 5 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

LoongArch: KVM: Fix stack protector issue in send_ipi_data()

Function kvm_io_bus_read() is called in function send_ipi_data(), buffer
size of parameter *val should be at least 8 bytes. Since some emulation
functions like loongarch_ipi_readl() and kvm_eiointc_read() will write
the buffer *val with 8 bytes signed extension regardless parameter len.

Otherwise there will be buffer overflow issue when CONFIG_STACKPROTECTOR
is enabled. The bug report is shown as follows:

Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: send_ipi_data+0x194/0x1a0 [kvm]
CPU: 11 UID: 107 PID: 2692 Comm: CPU 0/KVM Not tainted 6.17.0-rc1+ #102 PREEMPT(full)
Stack : 9000000005901568 0000000000000000 9000000003af371c 900000013c68c000
        900000013c68f850 900000013c68f858 0000000000000000 900000013c68f998
        900000013c68f990 900000013c68f990 900000013c68f6c0 fffffffffffdb058
        fffffffffffdb0e0 900000013c68f858 911e1d4d39cf0ec2 9000000105657a00
        0000000000000001 fffffffffffffffe 0000000000000578 282049464555206e
        6f73676e6f6f4c20 0000000000000001 00000000086b4000 0000000000000000
        0000000000000000 0000000000000000 9000000005709968 90000000058f9000
        900000013c68fa68 900000013c68fab4 90000000029279f0 900000010153f940
        900000010001f360 0000000000000000 9000000003af3734 000000004390000c
        00000000000000b0 0000000000000004 0000000000000000 0000000000071c1d
        ...
Call Trace:
[<9000000003af3734>] show_stack+0x5c/0x180
[<9000000003aed168>] dump_stack_lvl+0x6c/0x9c
[<9000000003ad0ab0>] vpanic+0x108/0x2c4
[<9000000003ad0ca8>] panic+0x3c/0x40
[<9000000004eb0a1c>] __stack_chk_fail+0x14/0x18
[<ffff8000023473f8>] send_ipi_data+0x190/0x1a0 [kvm]
[<ffff8000023313e4>] __kvm_io_bus_write+0xa4/0xe8 [kvm]
[<ffff80000233147c>] kvm_io_bus_write+0x54/0x90 [kvm]
[<ffff80000233f9f8>] kvm_emu_iocsr+0x180/0x310 [kvm]
[<ffff80000233fe08>] kvm_handle_gspr+0x280/0x478 [kvm]
[<ffff8000023443e8>] kvm_handle_exit+0xc0/0x130 [kvm]

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2025-39704?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39704?

Apply the vendor's patch.

## Is CVE-2025-39704 being exploited?

There is no known exploitation of CVE-2025-39704 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39704 and fix it if it is affected.

What it is: CVE-2025-39704 is a high-severity memory corruption vulnerability in Linux kernel, published on 5 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-39704 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-39704/ (Markdown: https://insights.sbomify.com/CVE-2025-39704/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39704
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39704
- OSV: https://osv.dev/vulnerability/CVE-2025-39704

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39704/
Summaries are generated and may contain mistakes; the official description above is the record.