CVE-2026-29008
U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
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
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
CVE-2026-29008- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-191
- Updated
- 2026-11-02
EUVDEUVD-2026-42332
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
EUVD-2026-42332- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-3qwj-q697-4ppr
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the...
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
GHSA-3qwj-q697-4ppr- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-191
- Updated
- 2026-11-02
NVD
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
CVE-2026-29008- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-191
- Updated
- 2026-11-02
OSV
U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
CVE-2026-29008- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-191
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-29008
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
DEBIAN-CVE-2026-29008- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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-2026-29008
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
- Record
UBUNTU-CVE-2026-29008- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
u-bootDebian: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 less2023.04~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-bootDebian:13 |
All versions, plus listed versions 2025.01-32025.01-3+deb13u12025.01-3.12025.01-3.2 |
None known |
u-bootDebian:14 |
All versions, plus listed versions 2025.01-32025.01-3.12025.01-3.2 |
None known |
u-bootUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 2015.04+dfsg1-2ubuntu12015.10+dfsg1-22015.10+dfsg1-32015.10+dfsg1-42016.01+dfsg1-1 Show 7 moreShow less2016.01+dfsg1-1ubuntu12016.01+dfsg1-2ubuntu12016.01+dfsg1-2ubuntu22016.01+dfsg1-2ubuntu32016.01+dfsg1-2ubuntu52016.01+dfsg1-2ubuntu5+esm12016.01+dfsg1-2ubuntu5+esm2 |
None known |
u-bootUbuntu:Pro:18.04:LTS |
All versions, 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-1ubuntu4~18.04.1 Show 4 moreShow less2020.10+dfsg-1ubuntu0~18.04.22020.10+dfsg-1ubuntu0~18.04.32020.10+dfsg-1ubuntu0~18.04.3+esm12020.10+dfsg-1ubuntu0~18.04.3+esm2 |
None known |
u-bootUbuntu:Pro:20.04:LTS |
All versions, 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 6 moreShow less2021.01+dfsg-3ubuntu0~20.04.32021.01+dfsg-3ubuntu0~20.04.42021.01+dfsg-3ubuntu0~20.04.52021.01+dfsg-3ubuntu0~20.04.62021.01+dfsg-3ubuntu0~20.04.6+esm12021.01+dfsg-3ubuntu0~20.04.6+esm2 |
None known |
u-bootUbuntu:22.04:LTS |
All versions, plus listed versions 2021.07+dfsg-0ubuntu82021.07+dfsg-0ubuntu92021.07+dfsg-0ubuntu102022.01+dfsg-2ubuntu12022.01+dfsg-2ubuntu2 Show 8 moreShow less2022.01+dfsg-2ubuntu2.12022.01+dfsg-2ubuntu2.32022.01+dfsg-2ubuntu2.42022.01+dfsg-2ubuntu2.52022.01+dfsg-2ubuntu2.62022.01+dfsg-2ubuntu2.72022.01+dfsg-2ubuntu2.82022.01+dfsg-2ubuntu2.9 |
None known |
u-boot-nezhaUbuntu: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-bootUbuntu:24.04:LTS |
All versions, plus listed versions 2023.07+dfsg-1ubuntu22024.01+dfsg-1ubuntu12024.01+dfsg-1ubuntu22024.01+dfsg-1ubuntu32024.01+dfsg-1ubuntu4 Show 9 moreShow less2024.01+dfsg-1ubuntu52024.01+dfsg-1ubuntu5.12024.01+dfsg-1ubuntu5.22025.01-0ubuntu0.24.04.12025.01-0ubuntu0.24.04.22025.10-0ubuntu0.24.04.12025.10-0ubuntu0.24.04.22025.10-0ubuntu0.24.04.32025.10-0ubuntu0.24.04.4 |
None known |
u-boot-nezhaUbuntu: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-bootUbuntu:25.10 |
All versions, plus listed versions 2025.01-1~0ubuntu22025.01-3ubuntu12025.01-3ubuntu22025.01-3ubuntu42025.10-0ubuntu0.25.10.1 |
None known |
u-bootUbuntu:26.10 |
All versions, plus listed versions 2025.10-0ubuntu22025.10-0ubuntu32025.10-0ubuntu42025.10-0ubuntu52025.10-0ubuntu6 |
None known |
u-bootUbuntu:26.04:LTS |
All versions, plus listed versions 2025.01-3ubuntu42025.10-0ubuntu12025.10-0ubuntu22025.10-0ubuntu2.12025.10-0ubuntu2.2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-29008 is a high vulnerability (CVSS 8.7) in Denx U-boot, published July 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.71%, the 53rd percentile. No source names a fixed version.