CVE-2026-71971: U-Boot before 2026.10-rc3 Out-of-Bounds Write in IP Fragment Reassembly

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-29 · updated 2026-09-30
Weakness: CWE-787

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

u-boot: before 2026.10-rc3 — fixed in 2026.10-rc3

How to fix

Upgrade to a fixed version: u-boot 2026.10-rc3. Check the vendor advisory for mitigations.

References

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/commit/04ca915d5bf39dda5d1bce62d04d2b59d293c5b9
https://www.vulncheck.com/advisories/u-boot-before-2026.10-rc3-out-of-bounds-write-in-ip-fragment-reassembly

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