Description
U-Boot before 2026.10-rc3 with CONFIG_IP_DEFRAG enabled contains an out-of-bounds write vulnerability in the __net_defragment() function in net/net.c. Remote attackers can send a crafted IP fragment with non-zero offset and More-Fragments flag set during netboot to corrupt adjacent memory and crash the bootloader.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| u-boot | u-boot | < 2026.10-rc3 | 2026.10-rc3 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | u-boot | No fix yet | — |
| Debian 13 | u-boot | No fix yet | — |
| Debian 12 | u-boot | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | u-boot | 2025.10-0ubuntu5 | — |
| Ubuntu 26.04 LTS | u-boot | 2025.10-0ubuntu2.1 | USN-8884-1 |
| Ubuntu 24.04 LTS | u-boot | 2025.10-0ubuntu0.24.04.3 | USN-8884-1 |
| Ubuntu 24.04 LTS | u-boot-nezha | No fix yet | — |
| Ubuntu 22.04 LTS | u-boot | 2022.01+dfsg-2ubuntu2.8 | USN-8884-1 |
| Ubuntu 22.04 LTS | u-boot-nezha | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | u-boot | 2021.01+dfsg-3ubuntu0~20.04.6+esm1 | USN-8884-1 |
| Ubuntu Pro 18.04 LTS | u-boot | 2020.10+dfsg-1ubuntu0~18.04.3+esm1 | USN-8884-1 |
| Ubuntu Pro 16.04 LTS | u-boot | 2016.01+dfsg1-2ubuntu5+esm1 | USN-8884-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | qemu | No fix yet | — |
Advisories 2
- WID-SEC-2026-3660 DENX U-Boot: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 21, 2026
- USN-8884-1 u-boot vulnerabilities Ubuntu Security Notices (USN) · Oct 7, 2026
References
- https://github.com/u-boot/u-boot/commit/04ca915d5bf39dda5d1bce62d04d2b59d293c5b9 patch
- https://github.com/u-boot/u-boot/blob/v2026.07/net/net.c#L975 technical-description
- https://github.com/u-boot/u-boot product
- VulnCheck Advisory: U-Boot before 2026.10-rc3 Out-of-Bounds Write in IP Fragment Reassembly third-party-advisory