# CVE-2025-21680: pktgen: Avoid out-of-bounds access in get_imix_entries

> A local attacker can trigger an out-of-bounds write in the Linux kernel pktgen module, potentially causing a crash or arbitrary code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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:** 31 Jan 2025
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-56375, AZL-56406, BELL-CVE-2025-21680, DEBIAN-CVE-2025-21680, GHSA-8qfw-mmqm-63gq, UBUNTU-CVE-2025-21680

## What is CVE-2025-21680?

CVE-2025-21680 is a high-severity memory corruption vulnerability in Linux kernel, published on 31 Jan 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:

pktgen: Avoid out-of-bounds access in get_imix_entries

Passing a sufficient amount of imix entries leads to invalid access to the
pkt_dev->imix_entries array because of the incorrect boundary check.

UBSAN: array-index-out-of-bounds in net/core/pktgen.c:874:24
index 20 is out of range for type 'imix_pkt [20]'
CPU: 2 PID: 1210 Comm: bash Not tainted 6.10.0-rc1 #121
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Call Trace:
<TASK>
dump_stack_lvl lib/dump_stack.c:117
__ubsan_handle_out_of_bounds lib/ubsan.c:429
get_imix_entries net/core/pktgen.c:874
pktgen_if_write net/core/pktgen.c:1063
pde_write fs/proc/inode.c:334
proc_reg_write fs/proc/inode.c:346
vfs_write fs/read_write.c:593
ksys_write fs/read_write.c:644
do_syscall_64 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe arch/x86/entry/entry_64.S:130

Found by Linux Verification Center (linuxtesting.org) with SVACE.

[ fp: allow to fill the array completely; minor changelog cleanup ]

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2025-21680?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21680?

Apply the vendor's patch.

## Is CVE-2025-21680 being exploited?

There is no known exploitation of CVE-2025-21680 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-2025-21680 and fix it if it is affected.

What it is: CVE-2025-21680 is a high-severity memory corruption vulnerability in Linux kernel, published on 31 Jan 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-2025-21680 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-2025-21680/ (Markdown: https://insights.sbomify.com/CVE-2025-21680/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21680
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21680
- OSV: https://osv.dev/vulnerability/CVE-2025-21680

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21680/
Summaries are generated and may contain mistakes; the official description above is the record.