---
title: "CVE-2026-71971: U-Boot - Denial of Service"
description: "U-Boot before 2026.10-rc3 with CONFIG_IP_DEFRAG enabled contains an out-of-bounds write caused by improper handling of crafted IP fragments in __net_defragment() function, letting remote attackers crash the bootloader via memory corruption, exploit requires network access during netboot."
url: https://panop.io/threat-heartbeat/CVE-2026-71971/
---

# CVE-2026-71971 U-Boot - Denial of Service

U-Boot before 2026.10-rc3 with CONFIG\_IP\_DEFRAG enabled contains an out-of-bounds write caused by improper handling of crafted IP fragments in \_\_net\_defragment() function, letting remote attackers crash the bootloader via memory corruption, exploit requires network access during netboot.

CVSS base score 8.2 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.38% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-71971)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Published

29 September 2026

Updated

15 October 2026

Weakness

[CWE-787](https://cwe.mitre.org/data/definitions/787.html)

## Vendor fix

Update to version 2026.10-rc3 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-71971](https://nvd.nist.gov/vuln/detail/CVE-2026-71971)
- [https://github.com/u-boot/u-boot](https://github.com/u-boot/u-boot)
- [https://github.com/u-boot/u-boot/blob/v2026.07/net/net.c#L975](https://github.com/u-boot/u-boot/blob/v2026.07/net/net.c#L975)
- [https://github.com/u-boot/u-boot/commit/04ca915d5bf39dda5d1bce62d04d2b59d293c5b9](https://github.com/u-boot/u-boot/commit/04ca915d5bf39dda5d1bce62d04d2b59d293c5b9)
- [https://www.vulncheck.com/advisories/u-boot-before-2026.10-rc3-out-of-bounds-write-in-ip-fragment-reassembly](https://www.vulncheck.com/advisories/u-boot-before-2026.10-rc3-out-of-bounds-write-in-ip-fragment-reassembly)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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