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CVE-2026-71971

U-Boot before 2026.10-rc3 Out-of-Bounds Write in IP Fragment Reassembly

8.8 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
High

Exploit likelihood

0.38%Unchanged since Sep 30, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.8

U-Boot before 2026.10-rc3 Out-of-Bounds Write in IP Fragment Reassembly

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.

Record
CVE-2026-71971
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-787
Updated
2026-11-02
EUVDEUVD-2026-89429 8.8

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.

Record
EUVD-2026-89429
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-9gg4-qrm6-f795 8.8

U-Boot before 2026.10-rc3 with CONFIG_IP_DEFRAG enabled contains an out-of-bounds write...

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.

Record
GHSA-9gg4-qrm6-f795
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-787
Updated
2026-11-02
NVD 8.8

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.

Record
CVE-2026-71971
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Weakness
CWE-787
Updated
2026-11-02
OSV 8.8

U-Boot before 2026.10-rc3 Out-of-Bounds Write in IP Fragment Reassembly

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.

Record
CVE-2026-71971
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-787
Updated
2026-11-02
OSVDEBIAN-CVE-2026-71971 8.8

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.

Record
DEBIAN-CVE-2026-71971
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Updated
2026-11-02
OSVUBUNTU-CVE-2026-71971 8.8

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.

Record
UBUNTU-CVE-2026-71971
CVSS 4.0
8.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
8.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Updated
2026-11-02
OSVAZL-105711 No score

CVE-2026-71971 affecting package qemu 10.1.0-1

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.

Record
AZL-105711
Updated
2026-11-02
OSVUSN-8884-1 No score

u-boot vulnerabilities

Timo Preißl discovered that U-Boot incorrectly handled certain malformed ZFS file system metadata. An attacker could possibly use this issue to trigger an integer overflow and out-of-bounds memory access, resulting in arbitrary code execution or a denial of service. (CVE-2025-70290)

Timo Preißl discovered that U-Boot incorrectly calculated buffer sizes when processing certain ext4 file systems. An attacker could possibly use this issue to trigger an integer overflow and out-of-bounds memory access, resulting in arbitrary code execution or a denial of service. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2025-70293)

Mateusz Furdyna discovered that U-Boot incorrectly handled certain fragmented IP traffic when IP defragmentation was enabled. An attacker could possibly use this issue to corrupt memory by sending crafted IP fragments, resulting in arbitrary code execution. (CVE-2026-15390)

Shahriyar Jalayeri and Mehrun P. Hunter discovered that U-Boot incorrectly handled certain fragmented IP traffic during network boot when IP defragmentation was enabled. An attacker could possibly use this issue to trigger an out-of-bounds write, resulting in a denial of service. (CVE-2026-71971)

Record
USN-8884-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
qemu
Azure Linux:3
 through 10.1.0-1 None known
u-boot
Debian:12
 All versions, plus listed versions
2023.01+dfsg-22023.01+dfsg-2+deb12u12023.01+dfsg-2+deb12u22023.01+dfsg-2+deb12u32023.04+dfsg-1
Show 19 moreShow less
2023.04~rc2+dfsg-12023.04~rc5+dfsg-12023.07+dfsg-12023.07~rc4+dfsg-12023.07~rc5+dfsg-12024.01+dfsg-12024.01+dfsg-22024.01+dfsg-32024.01+dfsg-42024.01+dfsg-52024.01+dfsg-62024.01+dfsg-72024.01~rc6+dfsg-12024.01~rc6+dfsg-22025.01-12025.01-22025.01-32025.01-3.12025.01-3.2
 None known
u-boot
Debian:13
 All versions, plus listed versions
2025.01-32025.01-3+deb13u12025.01-3.12025.01-3.2
 None known
u-boot
Debian:14
 All versions, plus listed versions
2025.01-32025.01-3.12025.01-3.2
 None known
u-boot
Ubuntu:Pro:16.04:LTS
 before 2016.01+dfsg1-2ubuntu5+esm1, plus listed versions
2015.04+dfsg1-2ubuntu12015.10+dfsg1-22015.10+dfsg1-32015.10+dfsg1-42016.01+dfsg1-1
Show 5 moreShow less
2016.01+dfsg1-1ubuntu12016.01+dfsg1-2ubuntu12016.01+dfsg1-2ubuntu22016.01+dfsg1-2ubuntu32016.01+dfsg1-2ubuntu5
2016.01+dfsg1-2ubuntu5+esm1
u-boot
Ubuntu:Pro:18.04:LTS
 before 2020.10+dfsg-1ubuntu0~18.04.3+esm1, plus listed versions
2016.03+dfsg1-6ubuntu22018.07~rc3+dfsg1-0ubuntu1~18.04.12018.07~rc3+dfsg1-0ubuntu2~18.04.12018.07~rc3+dfsg1-0ubuntu3~18.04.12019.07+dfsg-1ubuntu4~18.04.12020.10+dfsg-1ubuntu0~18.04.22020.10+dfsg-1ubuntu0~18.04.3
2020.10+dfsg-1ubuntu0~18.04.3+esm1
u-boot
Ubuntu:Pro:20.04:LTS
 before 2021.01+dfsg-3ubuntu0~20.04.6+esm1, plus listed versions
2019.07+dfsg-1ubuntu32019.07+dfsg-1ubuntu52019.07+dfsg-1ubuntu62020.10+dfsg-1ubuntu0~20.04.22021.01+dfsg-3ubuntu0~20.04.1
Show 4 moreShow less
2021.01+dfsg-3ubuntu0~20.04.32021.01+dfsg-3ubuntu0~20.04.42021.01+dfsg-3ubuntu0~20.04.52021.01+dfsg-3ubuntu0~20.04.6
2021.01+dfsg-3ubuntu0~20.04.6+esm1
u-boot
Ubuntu:22.04:LTS
 before 2022.01+dfsg-2ubuntu2.8, plus listed versions
2021.07+dfsg-0ubuntu82021.07+dfsg-0ubuntu92021.07+dfsg-0ubuntu102022.01+dfsg-2ubuntu12022.01+dfsg-2ubuntu2
Show 6 moreShow less
2022.01+dfsg-2ubuntu2.12022.01+dfsg-2ubuntu2.32022.01+dfsg-2ubuntu2.42022.01+dfsg-2ubuntu2.52022.01+dfsg-2ubuntu2.62022.01+dfsg-2ubuntu2.7
2022.01+dfsg-2ubuntu2.8
u-boot-nezha
Ubuntu:22.04:LTS
 All versions, plus listed versions
2021.09+git20211008.62392d3-0ubuntu12022.04+git20220405.7446a472-0ubuntu0.12022.04+git20220405.7446a472-0ubuntu0.22022.04+git20220405.7446a472-0ubuntu0.32022.04+git20220405.7446a472-0ubuntu0.4
 None known
u-boot
Ubuntu:24.04:LTS
 before 2025.10-0ubuntu0.24.04.3, plus listed versions
2023.07+dfsg-1ubuntu22024.01+dfsg-1ubuntu12024.01+dfsg-1ubuntu22024.01+dfsg-1ubuntu32024.01+dfsg-1ubuntu4
Show 7 moreShow less
2024.01+dfsg-1ubuntu52024.01+dfsg-1ubuntu5.12024.01+dfsg-1ubuntu5.22025.01-0ubuntu0.24.04.12025.01-0ubuntu0.24.04.22025.10-0ubuntu0.24.04.12025.10-0ubuntu0.24.04.2
2025.10-0ubuntu0.24.04.3
u-boot-nezha
Ubuntu:24.04:LTS
 All versions, plus listed versions
2022.10-1089-g528ae9bc6c-0ubuntu22024.01~rc1-190-g2e89b706f5-0ubuntu12024.01~rc1-190-g2e89b706f5-0ubuntu22024.01~rc1-190-g2e89b706f5-0ubuntu2.24.04.2
 None known
u-boot
Ubuntu:26.10
 before 2025.10-0ubuntu5, plus listed versions
2025.10-0ubuntu22025.10-0ubuntu32025.10-0ubuntu4
2025.10-0ubuntu5
u-boot
Ubuntu:26.04:LTS
 before 2025.10-0ubuntu2.1, plus listed versions
2025.01-3ubuntu42025.10-0ubuntu12025.10-0ubuntu2
2025.10-0ubuntu2.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-71971 is a high vulnerability (CVSS 8.8) in Denx Software Engineering U-boot, published September 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.38%, the 31st percentile. Fixed in u-boot 2016.01+dfsg1-2ubuntu5+esm1.

References

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