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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://lists.denx.de/pipermail/u-boot/2026-May/617853.html	Mailing List Third Party Advisory
https://u-boot.org/	Product
https://www.vulncheck.com/advisories/u-boot-rc3-integer-underflow-dos-via-tcp-rx-state-machine	Third Party Advisory Exploit
https://y637f9qq2x.com/posts/u-boot-tcp-nfs-vulns/	Third Party Advisory Exploit

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:denx:u-boot::::::::
	cpe:2.3:a:denx:u-boot:2026.04:rc1::::::
	cpe:2.3:a:denx:u-boot:2026.04:rc2::::::
	cpe:2.3:a:denx:u-boot:2026.04:rc3::::::

History

No history.

Information

Published : 2026-07-08 17:17

Updated : 2026-07-22 18:32

NVD link : CVE-2026-29008

Mitre link : CVE-2026-29008

CVE.ORG link : CVE-2026-29008

JSON object : View

Products Affected

denx

u-boot

CWE

CWE-191

Integer Underflow (Wrap or Wraparound)

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